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high severity
- Vulnerable module: tar
- Introduced through: tar.gz@1.0.7
Detailed paths
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › tar.gz@1.0.7 › tar@2.2.2
Overview
tar is a full-featured Tar for Node.js.
Affected versions of this package are vulnerable to Arbitrary File Write. node-tar
aims to guarantee that any file whose location would be modified by a symbolic link is not extracted. This is, in part, achieved by ensuring that extracted directories are not symlinks. Additionally, in order to prevent unnecessary stat calls to determine whether a given path is a directory, paths are cached when directories are created.
This logic was insufficient when extracting tar
files that contained both a directory and a symlink with the same name as the directory, where the symlink and directory names in the archive entry used backslashes as a path separator on posix systems. The cache checking logic used both \
and /
characters as path separators. However, \
is a valid filename character on posix systems.
By first creating a directory, and then replacing that directory with a symlink, it is possible to bypass node-tar
symlink checks on directories, essentially allowing an untrusted tar
file to symlink into an arbitrary location. This can lead to extracting arbitrary files into that location, thus allowing arbitrary file creation and overwrite.
Additionally, a similar confusion could arise on case-insensitive filesystems. If a tar
archive contained a directory at FOO
, followed by a symbolic link named foo
, then on case-insensitive file systems, the creation of the symbolic link would remove the directory from the filesystem, but not from the internal directory cache, as it would not be treated as a cache hit. A subsequent file entry within the FOO
directory would then be placed in the target of the symbolic link, thinking that the directory had already been created.
Remediation
Upgrade tar
to version 6.1.7, 5.0.8, 4.4.16 or higher.
References
high severity
- Vulnerable module: tar
- Introduced through: tar.gz@1.0.7
Detailed paths
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › tar.gz@1.0.7 › tar@2.2.2
Overview
tar is a full-featured Tar for Node.js.
Affected versions of this package are vulnerable to Arbitrary File Write. node-tar
aims to guarantee that any file whose location would be modified by a symbolic link is not extracted. This is, in part, achieved by ensuring that extracted directories are not symlinks. Additionally, in order to prevent unnecessary stat calls to determine whether a given path is a directory, paths are cached when directories are created.
This logic is insufficient when extracting tar
files that contain two directories and a symlink with names containing unicode values that normalized to the same value. Additionally, on Windows systems, long path portions would resolve to the same file system entities as their 8.3 "short path" counterparts.
A specially crafted tar
archive can include directories with two forms of the path that resolve to the same file system entity, followed by a symbolic link with a name in the first form, lastly followed by a file using the second form. This leads to bypassing node-tar
symlink checks on directories, essentially allowing an untrusted tar
file to symlink into an arbitrary location and extracting arbitrary files into that location.
Remediation
Upgrade tar
to version 6.1.9, 5.0.10, 4.4.18 or higher.
References
high severity
- Vulnerable module: tar
- Introduced through: tar.gz@1.0.7
Detailed paths
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › tar.gz@1.0.7 › tar@2.2.2
Overview
tar is a full-featured Tar for Node.js.
Affected versions of this package are vulnerable to Arbitrary File Write. node-tar
aims to guarantee that any file whose location would be outside of the extraction target directory is not extracted. This is, in part, accomplished by sanitizing absolute paths of entries within the archive, skipping archive entries that contain ..
path portions, and resolving the sanitized paths against the extraction target directory.
This logic is insufficient on Windows systems when extracting tar
files that contain a path that is not an absolute path, but specify a drive letter different from the extraction target, such as C:some\path
. If the drive letter does not match the extraction target, for example D:\extraction\dir
, then the result of path.resolve(extractionDirectory, entryPath)
resolves against the current working directory on the C:
drive, rather than the extraction target directory.
Additionally, a ..
portion of the path can occur immediately after the drive letter, such as C:../foo
, and is not properly sanitized by the logic that checks for ..
within the normalized and split portions of the path.
Note: This only affects users of node-tar
on Windows systems.
Remediation
Upgrade tar
to version 6.1.9, 5.0.10, 4.4.18 or higher.
References
high severity
- Vulnerable module: lodash
- Introduced through: plato@1.7.0
Detailed paths
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › lodash@4.13.1
Overview
lodash is a modern JavaScript utility library delivering modularity, performance, & extras.
Affected versions of this package are vulnerable to Prototype Pollution. The function zipObjectDeep
can be tricked into adding or modifying properties of the Object prototype. These properties will be present on all objects.
PoC
const _ = require('lodash');
_.zipObjectDeep(['__proto__.z'],[123]);
console.log(z); // 123
Details
Prototype Pollution is a vulnerability affecting JavaScript. Prototype Pollution refers to the ability to inject properties into existing JavaScript language construct prototypes, such as objects. JavaScript allows all Object attributes to be altered, including their magical attributes such as __proto__
, constructor
and prototype
. An attacker manipulates these attributes to overwrite, or pollute, a JavaScript application object prototype of the base object by injecting other values. Properties on the Object.prototype
are then inherited by all the JavaScript objects through the prototype chain. When that happens, this leads to either denial of service by triggering JavaScript exceptions, or it tampers with the application source code to force the code path that the attacker injects, thereby leading to remote code execution.
There are two main ways in which the pollution of prototypes occurs:
Unsafe
Object
recursive mergeProperty definition by path
Unsafe Object recursive merge
The logic of a vulnerable recursive merge function follows the following high-level model:
merge (target, source)
foreach property of source
if property exists and is an object on both the target and the source
merge(target[property], source[property])
else
target[property] = source[property]
When the source object contains a property named __proto__
defined with Object.defineProperty()
, the condition that checks if the property exists and is an object on both the target and the source passes and the merge recurses with the target, being the prototype of Object
and the source of Object
as defined by the attacker. Properties are then copied on the Object
prototype.
Clone operations are a special sub-class of unsafe recursive merges, which occur when a recursive merge is conducted on an empty object: merge({},source)
.
lodash
and Hoek
are examples of libraries susceptible to recursive merge attacks.
Property definition by path
There are a few JavaScript libraries that use an API to define property values on an object based on a given path. The function that is generally affected contains this signature: theFunction(object, path, value)
If the attacker can control the value of “path”, they can set this value to __proto__.myValue
. myValue
is then assigned to the prototype of the class of the object.
Types of attacks
There are a few methods by which Prototype Pollution can be manipulated:
Type | Origin | Short description |
---|---|---|
Denial of service (DoS) | Client | This is the most likely attack. DoS occurs when Object holds generic functions that are implicitly called for various operations (for example, toString and valueOf ). The attacker pollutes Object.prototype.someattr and alters its state to an unexpected value such as Int or Object . In this case, the code fails and is likely to cause a denial of service. For example: if an attacker pollutes Object.prototype.toString by defining it as an integer, if the codebase at any point was reliant on someobject.toString() it would fail. |
Remote Code Execution | Client | Remote code execution is generally only possible in cases where the codebase evaluates a specific attribute of an object, and then executes that evaluation. For example: eval(someobject.someattr) . In this case, if the attacker pollutes Object.prototype.someattr they are likely to be able to leverage this in order to execute code. |
Property Injection | Client | The attacker pollutes properties that the codebase relies on for their informative value, including security properties such as cookies or tokens. For example: if a codebase checks privileges for someuser.isAdmin , then when the attacker pollutes Object.prototype.isAdmin and sets it to equal true , they can then achieve admin privileges. |
Affected environments
The following environments are susceptible to a Prototype Pollution attack:
Application server
Web server
Web browser
How to prevent
Freeze the prototype— use
Object.freeze (Object.prototype)
.Require schema validation of JSON input.
Avoid using unsafe recursive merge functions.
Consider using objects without prototypes (for example,
Object.create(null)
), breaking the prototype chain and preventing pollution.As a best practice use
Map
instead ofObject
.
For more information on this vulnerability type:
Arteau, Oliver. “JavaScript prototype pollution attack in NodeJS application.” GitHub, 26 May 2018
Remediation
Upgrade lodash
to version 4.17.20 or higher.
References
high severity
- Vulnerable module: tar
- Introduced through: tar.gz@1.0.7
Detailed paths
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › tar.gz@1.0.7 › tar@2.2.2
Overview
tar is a full-featured Tar for Node.js.
Affected versions of this package are vulnerable to Arbitrary File Overwrite. This is due to insufficient symlink protection.
node-tar
aims to guarantee that any file whose location would be modified by a symbolic link is not extracted. This is, in part, achieved by ensuring that extracted directories are not symlinks. Additionally, in order to prevent unnecessary stat
calls to determine whether a given path is a directory, paths are cached when directories are created.
This logic is insufficient when extracting tar files that contain both a directory and a symlink with the same name as the directory. This order of operations results in the directory being created and added to the node-tar
directory cache. When a directory is present in the directory cache, subsequent calls to mkdir
for that directory are skipped.
However, this is also where node-tar
checks for symlinks occur. By first creating a directory, and then replacing that directory with a symlink, it is possible to bypass node-tar
symlink checks on directories, essentially allowing an untrusted tar file to symlink into an arbitrary location and subsequently extracting arbitrary files into that location.
Remediation
Upgrade tar
to version 3.2.3, 4.4.15, 5.0.7, 6.1.2 or higher.
References
high severity
- Vulnerable module: tar
- Introduced through: tar.gz@1.0.7
Detailed paths
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › tar.gz@1.0.7 › tar@2.2.2
Overview
tar is a full-featured Tar for Node.js.
Affected versions of this package are vulnerable to Arbitrary File Overwrite. This is due to insufficient absolute path sanitization.
node-tar
aims to prevent extraction of absolute file paths by turning absolute paths into relative paths when the preservePaths
flag is not set to true
. This is achieved by stripping the absolute path root from any absolute file paths contained in a tar file. For example, the path /home/user/.bashrc
would turn into home/user/.bashrc
.
This logic is insufficient when file paths contain repeated path roots such as ////home/user/.bashrc
. node-tar
only strips a single path root from such paths. When given an absolute file path with repeating path roots, the resulting path (e.g. ///home/user/.bashrc
) still resolves to an absolute path.
Remediation
Upgrade tar
to version 3.2.2, 4.4.14, 5.0.6, 6.1.1 or higher.
References
high severity
- Vulnerable module: ajv
- Introduced through: plato@1.7.0
Detailed paths
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › eslint@3.0.1 › table@3.8.3 › ajv@4.11.8
Overview
ajv is an Another JSON Schema Validator
Affected versions of this package are vulnerable to Prototype Pollution. A carefully crafted JSON schema could be provided that allows execution of other code by prototype pollution. (While untrusted schemas are recommended against, the worst case of an untrusted schema should be a denial of service, not execution of code.)
Details
Prototype Pollution is a vulnerability affecting JavaScript. Prototype Pollution refers to the ability to inject properties into existing JavaScript language construct prototypes, such as objects. JavaScript allows all Object attributes to be altered, including their magical attributes such as __proto__
, constructor
and prototype
. An attacker manipulates these attributes to overwrite, or pollute, a JavaScript application object prototype of the base object by injecting other values. Properties on the Object.prototype
are then inherited by all the JavaScript objects through the prototype chain. When that happens, this leads to either denial of service by triggering JavaScript exceptions, or it tampers with the application source code to force the code path that the attacker injects, thereby leading to remote code execution.
There are two main ways in which the pollution of prototypes occurs:
Unsafe
Object
recursive mergeProperty definition by path
Unsafe Object recursive merge
The logic of a vulnerable recursive merge function follows the following high-level model:
merge (target, source)
foreach property of source
if property exists and is an object on both the target and the source
merge(target[property], source[property])
else
target[property] = source[property]
When the source object contains a property named __proto__
defined with Object.defineProperty()
, the condition that checks if the property exists and is an object on both the target and the source passes and the merge recurses with the target, being the prototype of Object
and the source of Object
as defined by the attacker. Properties are then copied on the Object
prototype.
Clone operations are a special sub-class of unsafe recursive merges, which occur when a recursive merge is conducted on an empty object: merge({},source)
.
lodash
and Hoek
are examples of libraries susceptible to recursive merge attacks.
Property definition by path
There are a few JavaScript libraries that use an API to define property values on an object based on a given path. The function that is generally affected contains this signature: theFunction(object, path, value)
If the attacker can control the value of “path”, they can set this value to __proto__.myValue
. myValue
is then assigned to the prototype of the class of the object.
Types of attacks
There are a few methods by which Prototype Pollution can be manipulated:
Type | Origin | Short description |
---|---|---|
Denial of service (DoS) | Client | This is the most likely attack. DoS occurs when Object holds generic functions that are implicitly called for various operations (for example, toString and valueOf ). The attacker pollutes Object.prototype.someattr and alters its state to an unexpected value such as Int or Object . In this case, the code fails and is likely to cause a denial of service. For example: if an attacker pollutes Object.prototype.toString by defining it as an integer, if the codebase at any point was reliant on someobject.toString() it would fail. |
Remote Code Execution | Client | Remote code execution is generally only possible in cases where the codebase evaluates a specific attribute of an object, and then executes that evaluation. For example: eval(someobject.someattr) . In this case, if the attacker pollutes Object.prototype.someattr they are likely to be able to leverage this in order to execute code. |
Property Injection | Client | The attacker pollutes properties that the codebase relies on for their informative value, including security properties such as cookies or tokens. For example: if a codebase checks privileges for someuser.isAdmin , then when the attacker pollutes Object.prototype.isAdmin and sets it to equal true , they can then achieve admin privileges. |
Affected environments
The following environments are susceptible to a Prototype Pollution attack:
Application server
Web server
Web browser
How to prevent
Freeze the prototype— use
Object.freeze (Object.prototype)
.Require schema validation of JSON input.
Avoid using unsafe recursive merge functions.
Consider using objects without prototypes (for example,
Object.create(null)
), breaking the prototype chain and preventing pollution.As a best practice use
Map
instead ofObject
.
For more information on this vulnerability type:
Arteau, Oliver. “JavaScript prototype pollution attack in NodeJS application.” GitHub, 26 May 2018
Remediation
Upgrade ajv
to version 6.12.3 or higher.
References
high severity
- Vulnerable module: ansi-regex
- Introduced through: plato@1.7.0
Detailed paths
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › eslint@3.0.1 › inquirer@0.12.0 › ansi-regex@2.1.1
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › eslint@3.0.1 › chalk@1.1.3 › has-ansi@2.0.0 › ansi-regex@2.1.1
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › eslint@3.0.1 › chalk@1.1.3 › strip-ansi@3.0.1 › ansi-regex@2.1.1
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › eslint@3.0.1 › inquirer@0.12.0 › strip-ansi@3.0.1 › ansi-regex@2.1.1
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › eslint@3.0.1 › inquirer@0.12.0 › chalk@1.1.3 › has-ansi@2.0.0 › ansi-regex@2.1.1
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › eslint@3.0.1 › table@3.8.3 › chalk@1.1.3 › has-ansi@2.0.0 › ansi-regex@2.1.1
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › eslint@3.0.1 › inquirer@0.12.0 › chalk@1.1.3 › strip-ansi@3.0.1 › ansi-regex@2.1.1
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › eslint@3.0.1 › table@3.8.3 › chalk@1.1.3 › strip-ansi@3.0.1 › ansi-regex@2.1.1
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › eslint@3.0.1 › inquirer@0.12.0 › string-width@1.0.2 › strip-ansi@3.0.1 › ansi-regex@2.1.1
Overview
Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS) due to the sub-patterns [[\\]()#;?]*
and (?:;[-a-zA-Z\\d\\/#&.:=?%@~_]*)*
.
PoC
import ansiRegex from 'ansi-regex';
for(var i = 1; i <= 50000; i++) {
var time = Date.now();
var attack_str = "\u001B["+";".repeat(i*10000);
ansiRegex().test(attack_str)
var time_cost = Date.now() - time;
console.log("attack_str.length: " + attack_str.length + ": " + time_cost+" ms")
}
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
A
The string must start with the letter 'A'(B|C+)+
The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+
matches one or more times). The+
at the end of this section states that we can look for one or more matches of this section.D
Finally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD
, ABCCCCD
, ABCBCCCD
and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
String | Number of C's | Number of steps |
---|---|---|
ACCCX | 3 | 38 |
ACCCCX | 4 | 71 |
ACCCCCX | 5 | 136 |
ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade ansi-regex
to version 3.0.1, 4.1.1, 5.0.1, 6.0.1 or higher.
References
high severity
- Vulnerable module: async
- Introduced through: pkjutil@1.0.1
Detailed paths
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › pkjutil@1.0.1 › prod@1.0.1 › async-mixin@1.0.1 › async@2.0.1
Overview
Affected versions of this package are vulnerable to Prototype Pollution via the mapValues()
method, due to improper check in createObjectIterator
function.
PoC
//when objects are parsed, all properties are created as own (the objects can come from outside sources (http requests/ file))
const hasOwn = JSON.parse('{"__proto__": {"isAdmin": true}}');
//does not have the property, because it's inside object's own "__proto__"
console.log(hasOwn.isAdmin);
async.mapValues(hasOwn, (val, key, cb) => cb(null, val), (error, result) => {
// after the method executes, hasOwn.__proto__ value (isAdmin: true) replaces the prototype of the newly created object, leading to potential exploits.
console.log(result.isAdmin);
});
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 async
to version 2.6.4, 3.2.2 or higher.
References
high severity
- Vulnerable module: lodash
- Introduced through: plato@1.7.0
Detailed paths
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › lodash@4.13.1
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: mout
- Introduced through: tar.gz@1.0.7
Detailed paths
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › tar.gz@1.0.7 › mout@0.11.1
Overview
mout is a Modular Utilities
Affected versions of this package are vulnerable to Prototype Pollution. The deepFillIn
function can be used to 'fill missing properties recursively', while the deepMixIn
'mixes objects into the target object, recursively mixing existing child objects as well'. In both cases, the key used to access the target object recursively is not checked.
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 mout
to version 1.2.3 or higher.
References
high severity
- Vulnerable module: mout
- Introduced through: tar.gz@1.0.7
Detailed paths
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › tar.gz@1.0.7 › mout@0.11.1
Overview
mout is a Modular Utilities
Affected versions of this package are vulnerable to Prototype Pollution. The deepFillIn
function can be used to 'fill missing properties recursively', while the deepMixIn
mixes objects into the target object, recursively mixing existing child objects as well. In both cases, the key used to access the target object recursively is not checked, leading to exploiting this vulnerability.
Note: This vulnerability derives from an incomplete fix of CVE-2020-7792.
PoC
let mout = require("mout")
let b = {};
let payload = JSON.parse('["constructor.prototype.polluted"]');
mout.object.set(b, payload, "success");
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 mout
to version 1.2.4 or higher.
References
high severity
- Vulnerable module: taffydb
- Introduced through: @haixing_hu/jsdoc-minami@1.5.1
Detailed paths
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › @haixing_hu/jsdoc-minami@1.5.1 › taffydb@2.7.3
Overview
taffydb is an open source JavaScript library that provides in-memory database capabilities
Affected versions of this package are vulnerable to Internal Property Tampering. taffy
sets an internal index for each data item in its DB. However, it is found that the internal index can be forged by adding additional properties into user-input. If an index is found in the query, taffyDB
will ignore other query conditions and directly return the indexed data item. Moreover, the internal index is in an easily-guessable format (e.g. T000002R000001
). As such, attackers can use this vulnerability to access any data items in the DB and exploit an SQL Injection.
Note: The taffy package has been deprecated by the author. Its successor package, taffydb, is also found to be vulnerable and is not actively maintained.
PoC
var TAFFY = require('taffy');
var friends = TAFFY([
{"id":1,"gender":"M","username":"Smith","password":"aaa","status":"Active"},
{"id":2,"gender":"F","username":"Ruth","password":"bbb","status":"Active"},
{"id":3,"gender":"M","username":"Stevenson","password":"ccc","status":"Active"},
{"id":4,"gender":"F","username":"Gill","password":"ddd","status":"Active"}
]);
var json = {username:"Smith", "password":"123", "___id":"T000002R000002", "___s":true};
var item1 = friends(json);
console.log(item1.first());
Remediation
There is no fixed version for taffydb
.
References
high severity
- Vulnerable module: lodash
- Introduced through: plato@1.7.0
Detailed paths
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › lodash@4.13.1
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: plato@1.7.0
Detailed paths
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › lodash@4.13.1
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: plato@1.7.0
Detailed paths
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › lodash@4.13.1
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: lodash
- Introduced through: plato@1.7.0
Detailed paths
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › lodash@4.13.1
Overview
lodash is a modern JavaScript utility library delivering modularity, performance, & extras.
Affected versions of this package are vulnerable to Code Injection via template
.
PoC
var _ = require('lodash');
_.template('', { variable: '){console.log(process.env)}; with(obj' })()
Remediation
Upgrade lodash
to version 4.17.21 or higher.
References
high severity
- Vulnerable module: shelljs
- Introduced through: plato@1.7.0
Detailed paths
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › eslint@3.0.1 › shelljs@0.6.1
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › jshint@2.9.7 › shelljs@0.3.0
Overview
shelljs is a wrapper for the Unix shell commands for Node.js.
Affected versions of this package are vulnerable to Improper Privilege Management. When ShellJS
is used to create shell scripts which may be running as root
, users with low-level privileges on the system can leak sensitive information such as passwords (depending on implementation) from the standard output of the privileged process OR shutdown privileged ShellJS
processes via the exec
function when triggering EACCESS errors.
Note: Thi only impacts the synchronous version of shell.exec()
.
Remediation
Upgrade shelljs
to version 0.8.5 or higher.
References
medium severity
- Vulnerable module: request
- Introduced through: pkjutil@1.0.1
Detailed paths
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › pkjutil@1.0.1 › bagofrequest@0.1.4 › 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: tar
- Introduced through: tar.gz@1.0.7
Detailed paths
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › tar.gz@1.0.7 › tar@2.2.2
Overview
tar is a full-featured Tar for Node.js.
Affected versions of this package are vulnerable to Uncontrolled Resource Consumption ('Resource Exhaustion') due to the lack of folders count validation during the folder creation process. An attacker who generates a large number of sub-folders can consume memory on the system running the software and even crash the client within few seconds of running it using a path with too many sub-folders inside.
Remediation
Upgrade tar
to version 6.2.1 or higher.
References
medium severity
- Vulnerable module: tough-cookie
- Introduced through: pkjutil@1.0.1
Detailed paths
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › pkjutil@1.0.1 › bagofrequest@0.1.4 › 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: lodash
- Introduced through: plato@1.7.0
Detailed paths
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › lodash@4.13.1
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: inflight
- Introduced through: mocha@10.8.2, plato@1.7.0 and others
Detailed paths
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › mocha@10.8.2 › glob@8.1.0 › inflight@1.0.6
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › glob@7.0.6 › inflight@1.0.6
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › buildbranch@2.0.1 › rimraf@2.7.1 › glob@7.2.3 › inflight@1.0.6
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › cmdt@1.0.0 › rimraf@2.7.1 › glob@7.2.3 › inflight@1.0.6
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › eslint@3.0.1 › glob@7.2.3 › inflight@1.0.6
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › ae86@3.1.0 › cpr@3.0.1 › rimraf@2.7.1 › glob@7.2.3 › inflight@1.0.6
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › cmdt@1.0.0 › fs-extra@0.30.0 › rimraf@2.7.1 › glob@7.2.3 › inflight@1.0.6
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › fs-extra@0.30.0 › rimraf@2.7.1 › glob@7.2.3 › inflight@1.0.6
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › tar.gz@1.0.7 › fstream@1.0.12 › rimraf@2.7.1 › glob@7.2.3 › inflight@1.0.6
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › jshint@2.9.7 › cli@1.0.1 › glob@7.2.3 › inflight@1.0.6
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › tar.gz@1.0.7 › tar@2.2.2 › fstream@1.0.12 › rimraf@2.7.1 › glob@7.2.3 › inflight@1.0.6
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › madge@8.0.0 › dependency-tree@11.0.1 › filing-cabinet@5.0.2 › module-lookup-amd@9.0.2 › glob@7.2.3 › inflight@1.0.6
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › pkjutil@1.0.1 › prod@1.0.1 › read-installed@4.0.3 › read-package-json@2.1.2 › glob@7.2.3 › inflight@1.0.6
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › eslint@3.0.1 › file-entry-cache@1.3.1 › flat-cache@1.3.4 › rimraf@2.6.3 › glob@7.2.3 › inflight@1.0.6
Overview
Affected versions of this package are vulnerable to Missing Release of Resource after Effective Lifetime via the makeres
function due to improperly deleting keys from the reqs
object after execution of callbacks. This behavior causes the keys to remain in the reqs
object, which leads to resource exhaustion.
Exploiting this vulnerability results in crashing the node
process or in the application crash.
Note: This library is not maintained, and currently, there is no fix for this issue. To overcome this vulnerability, several dependent packages have eliminated the use of this library.
To trigger the memory leak, an attacker would need to have the ability to execute or influence the asynchronous operations that use the inflight module within the application. This typically requires access to the internal workings of the server or application, which is not commonly exposed to remote users. Therefore, “Attack vector” is marked as “Local”.
PoC
const inflight = require('inflight');
function testInflight() {
let i = 0;
function scheduleNext() {
let key = `key-${i++}`;
const callback = () => {
};
for (let j = 0; j < 1000000; j++) {
inflight(key, callback);
}
setImmediate(scheduleNext);
}
if (i % 100 === 0) {
console.log(process.memoryUsage());
}
scheduleNext();
}
testInflight();
Remediation
There is no fixed version for inflight
.
References
medium severity
- Vulnerable module: lodash
- Introduced through: plato@1.7.0
Detailed paths
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › lodash@4.13.1
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: lodash
- Introduced through: plato@1.7.0
Detailed paths
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › lodash@4.13.1
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
- Module: escomplex-plugin-metrics-module
- Introduced through: plato@1.7.0
Detailed paths
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › typhonjs-escomplex@0.0.9 › typhonjs-escomplex-module@0.0.9 › escomplex-plugin-metrics-module@0.0.10
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › typhonjs-escomplex@0.0.9 › typhonjs-escomplex-project@0.0.9 › typhonjs-escomplex-module@0.0.9 › escomplex-plugin-metrics-module@0.0.10
MPL-2.0 license
medium severity
- Module: escomplex-plugin-metrics-project
- Introduced through: plato@1.7.0
Detailed paths
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › typhonjs-escomplex@0.0.9 › typhonjs-escomplex-project@0.0.9 › escomplex-plugin-metrics-project@0.0.10
MPL-2.0 license
medium severity
- Module: escomplex-plugin-syntax-babylon
- Introduced through: plato@1.7.0
Detailed paths
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › typhonjs-escomplex@0.0.9 › typhonjs-escomplex-module@0.0.9 › escomplex-plugin-syntax-babylon@0.0.10
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › typhonjs-escomplex@0.0.9 › typhonjs-escomplex-project@0.0.9 › typhonjs-escomplex-module@0.0.9 › escomplex-plugin-syntax-babylon@0.0.10
MPL-2.0 license
medium severity
- Module: escomplex-plugin-syntax-estree
- Introduced through: plato@1.7.0
Detailed paths
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › typhonjs-escomplex@0.0.9 › typhonjs-escomplex-module@0.0.9 › escomplex-plugin-syntax-babylon@0.0.10 › escomplex-plugin-syntax-estree@0.0.10
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › typhonjs-escomplex@0.0.9 › typhonjs-escomplex-project@0.0.9 › typhonjs-escomplex-module@0.0.9 › escomplex-plugin-syntax-babylon@0.0.10 › escomplex-plugin-syntax-estree@0.0.10
MPL-2.0 license
medium severity
- Module: postcss-values-parser
- Introduced through: madge@8.0.0
Detailed paths
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › madge@8.0.0 › dependency-tree@11.0.1 › precinct@12.1.2 › detective-postcss@7.0.0 › postcss-values-parser@6.0.2
MPL-2.0 license
medium severity
- Module: typhonjs-ast-walker
- Introduced through: plato@1.7.0
Detailed paths
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › typhonjs-escomplex@0.0.9 › typhonjs-escomplex-module@0.0.9 › typhonjs-ast-walker@0.1.1
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › typhonjs-escomplex@0.0.9 › typhonjs-escomplex-project@0.0.9 › typhonjs-escomplex-module@0.0.9 › typhonjs-ast-walker@0.1.1
MPL-2.0 license
medium severity
- Module: typhonjs-escomplex
- Introduced through: plato@1.7.0
Detailed paths
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › typhonjs-escomplex@0.0.9
MPL-2.0 license
medium severity
- Module: typhonjs-escomplex-commons
- Introduced through: plato@1.7.0
Detailed paths
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › typhonjs-escomplex@0.0.9 › typhonjs-escomplex-module@0.0.9 › typhonjs-escomplex-commons@0.0.14
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › typhonjs-escomplex@0.0.9 › typhonjs-escomplex-project@0.0.9 › typhonjs-escomplex-commons@0.0.14
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › typhonjs-escomplex@0.0.9 › typhonjs-escomplex-module@0.0.9 › escomplex-plugin-metrics-module@0.0.10 › typhonjs-escomplex-commons@0.0.14
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › typhonjs-escomplex@0.0.9 › typhonjs-escomplex-module@0.0.9 › escomplex-plugin-syntax-babylon@0.0.10 › typhonjs-escomplex-commons@0.0.14
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › typhonjs-escomplex@0.0.9 › typhonjs-escomplex-project@0.0.9 › typhonjs-escomplex-module@0.0.9 › typhonjs-escomplex-commons@0.0.14
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › typhonjs-escomplex@0.0.9 › typhonjs-escomplex-project@0.0.9 › escomplex-plugin-metrics-project@0.0.10 › typhonjs-escomplex-commons@0.0.14
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › typhonjs-escomplex@0.0.9 › typhonjs-escomplex-project@0.0.9 › typhonjs-escomplex-module@0.0.9 › escomplex-plugin-metrics-module@0.0.10 › typhonjs-escomplex-commons@0.0.14
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › typhonjs-escomplex@0.0.9 › typhonjs-escomplex-module@0.0.9 › escomplex-plugin-syntax-babylon@0.0.10 › escomplex-plugin-syntax-estree@0.0.10 › typhonjs-escomplex-commons@0.0.14
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › typhonjs-escomplex@0.0.9 › typhonjs-escomplex-project@0.0.9 › typhonjs-escomplex-module@0.0.9 › escomplex-plugin-syntax-babylon@0.0.10 › typhonjs-escomplex-commons@0.0.14
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › typhonjs-escomplex@0.0.9 › typhonjs-escomplex-project@0.0.9 › typhonjs-escomplex-module@0.0.9 › escomplex-plugin-syntax-babylon@0.0.10 › escomplex-plugin-syntax-estree@0.0.10 › typhonjs-escomplex-commons@0.0.14
MPL-2.0 license
medium severity
- Module: typhonjs-escomplex-module
- Introduced through: plato@1.7.0
Detailed paths
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › typhonjs-escomplex@0.0.9 › typhonjs-escomplex-module@0.0.9
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › typhonjs-escomplex@0.0.9 › typhonjs-escomplex-project@0.0.9 › typhonjs-escomplex-module@0.0.9
MPL-2.0 license
medium severity
- Module: typhonjs-escomplex-project
- Introduced through: plato@1.7.0
Detailed paths
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › typhonjs-escomplex@0.0.9 › typhonjs-escomplex-project@0.0.9
MPL-2.0 license
medium severity
- Module: typhonjs-plugin-manager
- Introduced through: plato@1.7.0
Detailed paths
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › typhonjs-escomplex@0.0.9 › typhonjs-escomplex-module@0.0.9 › typhonjs-plugin-manager@0.0.3
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › typhonjs-escomplex@0.0.9 › typhonjs-escomplex-project@0.0.9 › typhonjs-plugin-manager@0.0.3
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › typhonjs-escomplex@0.0.9 › typhonjs-escomplex-project@0.0.9 › typhonjs-escomplex-module@0.0.9 › typhonjs-plugin-manager@0.0.3
MPL-2.0 license
low severity
- Vulnerable module: eslint
- Introduced through: plato@1.7.0
Detailed paths
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › plato@1.7.0 › eslint@3.0.1
Overview
eslint is a pluggable linting utility for JavaScript and JSX
Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS). This can cause an impact of about 10 seconds matching time for data 100k characters long.
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
A
The string must start with the letter 'A'(B|C+)+
The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+
matches one or more times). The+
at the end of this section states that we can look for one or more matches of this section.D
Finally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD
, ABCCCCD
, ABCBCCCD
and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
String | Number of C's | Number of steps |
---|---|---|
ACCCX | 3 | 38 |
ACCCCX | 4 | 71 |
ACCCCCX | 5 | 136 |
ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade eslint
to version 4.18.2 or higher.
References
low severity
- Vulnerable module: tar
- Introduced through: tar.gz@1.0.7
Detailed paths
-
Introduced through: bob@cliffano/bob#973dada26157f034ae6696804912a0c27a2d250f › tar.gz@1.0.7 › tar@2.2.2
Overview
tar is a full-featured Tar for Node.js.
Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS). When stripping the trailing slash from files
arguments, the f.replace(/\/+$/, '')
performance of this function can exponentially degrade when f
contains many /
characters resulting in ReDoS.
This vulnerability is not likely to be exploitable as it requires that the untrusted input is being passed into the tar.extract()
or tar.list()
array of entries to parse/extract, which would be unusual.
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 tar
to version 6.1.4, 5.0.8, 4.4.16 or higher.