steroids@4.0.10

Vulnerabilities

75 via 482 paths

Dependencies

665

Source

npm

Find, fix and prevent vulnerabilities in your code.

Severity
  • 4
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  • 27
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Status
  • 75
  • 0
  • 0

critical severity

Arbitrary File Write via Archive Extraction (Zip Slip)

  • Vulnerable module: decompress-zip
  • Introduced through: bower@1.3.8

Detailed paths

  • Introduced through: steroids@4.0.10 bower@1.3.8 decompress-zip@0.0.8
    Remediation: Upgrade to bower@1.7.5.

Overview

decompress-zip extracts the contents of the ZIP archive file.

Affected versions of this package are vulnerable to Arbitrary File Write via Archive Extraction (Zip Slip). The package will extract files outside of the scope of the specified target directory because there is no validation that file extraction stays within the defined target path.

Details

It is exploited using a specially crafted zip archive, that holds path traversal filenames. When exploited, a filename in a malicious archive is concatenated to the target extraction directory, which results in the final path ending up outside of the target folder. For instance, a zip may hold a file with a "../../file.exe" location and thus break out of the target folder. If an executable or a configuration file is overwritten with a file containing malicious code, the problem can turn into an arbitrary code execution issue quite easily.

The following is an example of a zip archive with one benign file and one malicious file. Extracting the malicous file will result in traversing out of the target folder, ending up in /root/.ssh/ overwriting the authorized_keys file:


+2018-04-15 22:04:29 ..... 19 19 good.txt

+2018-04-15 22:04:42 ..... 20 20 ../../../../../../root/.ssh/authorized_keys

Remediation

Upgrade decompress-zip to version 0.2.2, 0.3.2 or higher.

References

critical severity

Prototype Pollution

  • Vulnerable module: handlebars
  • Introduced through: bower@1.3.8

Detailed paths

  • Introduced through: steroids@4.0.10 bower@1.3.8 handlebars@1.3.0
    Remediation: Upgrade to bower@1.7.5.

Overview

handlebars is an extension to the Mustache templating language.

Affected versions of this package are vulnerable to Prototype Pollution. It is possible to add or modify properties to the Object prototype through a malicious template. This may allow attackers to crash the application or execute Arbitrary Code in specific conditions.

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 merge
  • Property 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

How to prevent

  1. Freeze the prototype— use Object.freeze (Object.prototype).
  2. Require schema validation of JSON input.
  3. Avoid using unsafe recursive merge functions.
  4. Consider using objects without prototypes (for example, Object.create(null)), breaking the prototype chain and preventing pollution.
  5. As a best practice use Map instead of Object.

For more information on this vulnerability type:

Arteau, Oliver. “JavaScript prototype pollution attack in NodeJS application.” GitHub, 26 May 2018

Remediation

Upgrade handlebars to version 4.5.3, 3.0.8 or higher.

References

critical severity

Prototype Pollution

  • Vulnerable module: lodash
  • Introduced through: yeoman-generator@0.17.7, bower@1.3.8 and others

Detailed paths

  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.23.0.
  • Introduced through: steroids@4.0.10 bower@1.3.8 inquirer@0.5.1 lodash@2.4.2
    Remediation: Upgrade to bower@1.7.5.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 cheerio@0.17.0 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.19.0.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 file-utils@0.2.2 lodash@2.4.2
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 findup-sync@0.1.3 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.21.0.
  • Introduced through: steroids@4.0.10 grunt@0.4.5 findup-sync@0.1.3 lodash@2.4.2
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 gruntfile-editor@0.2.0 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.19.0.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 inquirer@0.7.3 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.21.0.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 lodash@2.4.2
  • Introduced through: steroids@4.0.10 grunt@0.4.5 grunt-legacy-log@0.1.3 lodash@2.4.2
    Remediation: Upgrade to grunt@1.0.0.
  • Introduced through: steroids@4.0.10 bower@1.3.8 insight@0.3.1 inquirer@0.4.1 lodash@2.4.2
    Remediation: Upgrade to bower@1.7.5.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 cheerio@0.17.0 lodash@2.4.2
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 file-utils@0.2.2 lodash@2.4.2
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 findup-sync@0.1.3 lodash@2.4.2
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 gruntfile-editor@0.2.0 ast-query@0.2.5 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.19.0.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 gruntfile-editor@0.2.0 lodash@2.4.2
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 inquirer@0.7.3 lodash@2.4.2
  • Introduced through: steroids@4.0.10 grunt@0.4.5 grunt-legacy-log@0.1.3 grunt-legacy-log-utils@0.1.1 lodash@2.4.2
    Remediation: Upgrade to grunt@1.0.3.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 gruntfile-editor@0.2.0 ast-query@0.2.5 lodash@2.4.2
  • Introduced through: steroids@4.0.10 grunt@0.4.5 lodash@0.9.2
    Remediation: Upgrade to grunt@1.0.0.
  • Introduced through: steroids@4.0.10 grunt@0.4.5 grunt-legacy-util@0.2.0 lodash@0.9.2
    Remediation: Upgrade to grunt@1.0.3.
  • Introduced through: steroids@4.0.10 inquirer@0.3.4 lodash@1.2.1
    Remediation: Upgrade to inquirer@0.12.0.
  • Introduced through: steroids@4.0.10 lodash@2.4.1
    Remediation: Upgrade to lodash@4.17.20.

Overview

lodash is a modern JavaScript utility library delivering modularity, performance, & extras.

Affected versions of this package are vulnerable to Prototype Pollution in zipObjectDeep due to an incomplete fix for CVE-2020-8203.

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 merge
  • Property 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

How to prevent

  1. Freeze the prototype— use Object.freeze (Object.prototype).
  2. Require schema validation of JSON input.
  3. Avoid using unsafe recursive merge functions.
  4. Consider using objects without prototypes (for example, Object.create(null)), breaking the prototype chain and preventing pollution.
  5. As a best practice use Map instead of Object.

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

critical severity

Arbitrary Code Injection

  • Vulnerable module: open
  • Introduced through: open@0.0.4

Detailed paths

  • Introduced through: steroids@4.0.10 open@0.0.4
    Remediation: Upgrade to open@6.0.0.

Overview

open is a cross platform package that opens stuff like URLs, files, executables.

Affected versions of this package are vulnerable to Arbitrary Code Injection when unsanitized user input is passed in.

The package does come with the following warning in the readme:

The same care should be taken when calling open as if you were calling child_process.exec directly. If it is an executable it will run in a new shell.

The package open is replacing the opn package, which is now deprecated. The older versions of open are vulnerable.

Note: Upgrading open to the last version will prevent this vulnerability but is also likely to have unwanted effects since it now has a very different API.

Remediation

Upgrade open to version 6.0.0 or higher.

References

high severity

Directory Traversal

  • Vulnerable module: adm-zip
  • Introduced through: yeoman-generator@0.17.7 and generator-steroids@1.0.18

Detailed paths

  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-unzip@1.0.0 adm-zip@0.4.16
    Remediation: Upgrade to yeoman-generator@0.24.1.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-unzip@1.0.0 adm-zip@0.4.16

Overview

adm-zip is a JavaScript implementation for zip data compression for NodeJS.

Affected versions of this package are vulnerable to Directory Traversal. It could extract files outside the target folder.

Details

A Directory Traversal attack (also known as path traversal) aims to access files and directories that are stored outside the intended folder. By manipulating files with "dot-dot-slash (../)" sequences and its variations, or by using absolute file paths, it may be possible to access arbitrary files and directories stored on file system, including application source code, configuration, and other critical system files.

Directory Traversal vulnerabilities can be generally divided into two types:

  • Information Disclosure: Allows the attacker to gain information about the folder structure or read the contents of sensitive files on the system.

st is a module for serving static files on web pages, and contains a vulnerability of this type. In our example, we will serve files from the public route.

If an attacker requests the following URL from our server, it will in turn leak the sensitive private key of the root user.

curl http://localhost:8080/public/%2e%2e/%2e%2e/%2e%2e/%2e%2e/%2e%2e/root/.ssh/id_rsa

Note %2e is the URL encoded version of . (dot).

  • Writing arbitrary files: Allows the attacker to create or replace existing files. This type of vulnerability is also known as Zip-Slip.

One way to achieve this is by using a malicious zip archive that holds path traversal filenames. When each filename in the zip archive gets concatenated to the target extraction folder, without validation, the final path ends up outside of the target folder. If an executable or a configuration file is overwritten with a file containing malicious code, the problem can turn into an arbitrary code execution issue quite easily.

The following is an example of a zip archive with one benign file and one malicious file. Extracting the malicious file will result in traversing out of the target folder, ending up in /root/.ssh/ overwriting the authorized_keys file:

2018-04-15 22:04:29 .....           19           19  good.txt
2018-04-15 22:04:42 .....           20           20  ../../../../../../root/.ssh/authorized_keys

Remediation

Upgrade adm-zip to version 0.5.2 or higher.

References

high severity

Regular Expression Denial of Service (ReDoS)

  • Vulnerable module: ansi-regex
  • Introduced through: npm@2.1.7

Detailed paths

  • Introduced through: steroids@4.0.10 npm@2.1.7 npm-registry-client@4.0.5 npmlog@5.0.1 gauge@3.0.1 strip-ansi@4.0.0 ansi-regex@3.0.0
  • Introduced through: steroids@4.0.10 npm@2.1.7 npm-registry-client@4.0.5 npmlog@5.0.1 gauge@3.0.1 string-width@2.1.1 strip-ansi@4.0.0 ansi-regex@3.0.0

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:

  1. CCC
  2. CC+C
  3. C+CC
  4. 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 6.0.1, 5.0.1 or higher.

References

high severity

Remote Memory Exposure

  • Vulnerable module: bl
  • Introduced through: npm@2.1.7 and bower@1.3.8

Detailed paths

  • Introduced through: steroids@4.0.10 npm@2.1.7 request@2.47.0 bl@0.9.5
    Remediation: Upgrade to npm@3.0.0.
  • Introduced through: steroids@4.0.10 bower@1.3.8 bower-registry-client@0.2.4 request@2.51.0 bl@0.9.5
    Remediation: Upgrade to bower@1.6.2.

Overview

bl is a library that allows you to collect buffers and access with a standard readable buffer interface.

Affected versions of this package are vulnerable to Remote Memory Exposure. If user input ends up in consume() argument and can become negative, BufferList state can be corrupted, tricking it into exposing uninitialized memory via regular .slice() calls.

PoC by chalker

const { BufferList } = require('bl')
const secret = require('crypto').randomBytes(256)
for (let i = 0; i < 1e6; i++) {
  const clone = Buffer.from(secret)
  const bl = new BufferList()
  bl.append(Buffer.from('a'))
  bl.consume(-1024)
  const buf = bl.slice(1)
  if (buf.indexOf(clone) !== -1) {
    console.error(`Match (at ${i})`, buf)
  }
}

Remediation

Upgrade bl to version 2.2.1, 3.0.1, 4.0.3, 1.2.3 or higher.

References

high severity

Arbitrary File Write via Archive Extraction (Zip Slip)

  • Vulnerable module: bower
  • Introduced through: bower@1.3.8

Detailed paths

  • Introduced through: steroids@4.0.10 bower@1.3.8
    Remediation: Upgrade to bower@1.8.8.

Overview

bower offers a generic, unopinionated solution to the problem of front-end package management.

Affected versions of this package are vulnerable to Arbitrary File Write via Archive Extraction (Zip Slip). Attackers can write arbitrary files when a malicious archive is extracted.

Details

It is exploited using a specially crafted zip archive, that holds path traversal filenames. When exploited, a filename in a malicious archive is concatenated to the target extraction directory, which results in the final path ending up outside of the target folder. For instance, a zip may hold a file with a "../../file.exe" location and thus break out of the target folder. If an executable or a configuration file is overwritten with a file containing malicious code, the problem can turn into an arbitrary code execution issue quite easily.

The following is an example of a zip archive with one benign file and one malicious file. Extracting the malicous file will result in traversing out of the target folder, ending up in /root/.ssh/ overwriting the authorized_keys file:


+2018-04-15 22:04:29 ..... 19 19 good.txt

+2018-04-15 22:04:42 ..... 20 20 ../../../../../../root/.ssh/authorized_keys

Remediation

Upgrade bower to version 1.8.8 or higher.

References

high severity

Prototype Pollution

  • Vulnerable module: deep-extend
  • Introduced through: bower@1.3.8

Detailed paths

  • Introduced through: steroids@4.0.10 bower@1.3.8 bower-json@0.4.0 deep-extend@0.2.11
    Remediation: Upgrade to bower@1.7.5.

Overview

deep-extend is a library for Recursive object extending.

Affected versions of this package are vulnerable to Prototype Pollution. Utilities function in all the listed modules can be tricked into modifying the prototype of "Object" when the attacker control part of the structure passed to these function. This can let an attacker add or modify existing property that will exist on all object.

PoC by HoLyVieR

var merge = require('deep-extend');
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

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:

  1. CCC
  2. CC+C
  3. C+CC
  4. 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 deep-extend to version 0.5.1 or higher.

References

high severity

Regular Expression Denial of Service (ReDoS)

  • Vulnerable module: fresh
  • Introduced through: express@4.8.8

Detailed paths

  • Introduced through: steroids@4.0.10 express@4.8.8 fresh@0.2.2
    Remediation: Upgrade to express@4.15.5.
  • Introduced through: steroids@4.0.10 express@4.8.8 send@0.8.5 fresh@0.2.2
    Remediation: Upgrade to express@4.15.5.
  • Introduced through: steroids@4.0.10 express@4.8.8 serve-static@1.5.4 send@0.8.5 fresh@0.2.2
    Remediation: Upgrade to express@4.15.5.

Overview

fresh is HTTP response freshness testing.

Affected versions of this package are vulnerable to Regular expression Denial of Service (ReDoS) attacks. A Regular Expression (/ *, */) was used for parsing HTTP headers and take about 2 seconds matching time for 50k characters.

Details

Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.

The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.

Let’s take the following regular expression as an example:

regex = /A(B|C+)+D/

This regular expression accomplishes the following:

  • A The string must start with the letter 'A'
  • (B|C+)+ The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the + matches one or more times). The + at the end of this section states that we can look for one or more matches of this section.
  • D Finally, we ensure this section of the string ends with a 'D'

The expression would match inputs such as ABBD, ABCCCCD, ABCBCCCD and ACCCCCD

It most cases, it doesn't take very long for a regex engine to find a match:

$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total

$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total

The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.

Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.

Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:

  1. CCC
  2. CC+C
  3. C+CC
  4. C+C+C.

The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.

From there, the number of steps the engine must use to validate a string just continues to grow.

String Number of C's Number of steps
ACCCX 3 38
ACCCCX 4 71
ACCCCCX 5 136
ACCCCCCCCCCCCCCX 14 65,553

By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.

Remediation

Upgrade fresh to version 0.5.2 or higher.

References

high severity

Arbitrary File Overwrite

  • Vulnerable module: fstream
  • Introduced through: bower@1.3.8

Detailed paths

  • Introduced through: steroids@4.0.10 bower@1.3.8 fstream@0.1.31
    Remediation: Upgrade to bower@1.3.10.
  • Introduced through: steroids@4.0.10 bower@1.3.8 fstream-ignore@0.0.10 fstream@0.1.31
    Remediation: Upgrade to bower@1.3.10.
  • Introduced through: steroids@4.0.10 bower@1.3.8 tar@0.1.20 fstream@0.1.31
    Remediation: Upgrade to bower@1.3.10.

Overview

fstream is a package that supports advanced FS Streaming for Node.

Affected versions of this package are vulnerable to Arbitrary File Overwrite. Extracting tarballs containing a hardlink to a file that already exists in the system and a file that matches the hardlink will overwrite the system's file with the contents of the extracted file.

Remediation

Upgrade fstream to version 1.0.12 or higher.

References

high severity

Prototype Pollution

  • Vulnerable module: getobject
  • Introduced through: grunt@0.4.5

Detailed paths

  • Introduced through: steroids@4.0.10 grunt@0.4.5 getobject@0.1.0
    Remediation: Upgrade to grunt@1.0.0.
  • Introduced through: steroids@4.0.10 grunt@0.4.5 grunt-legacy-util@0.2.0 getobject@0.1.0
    Remediation: Upgrade to grunt@1.3.0.

Overview

Affected versions of this package are vulnerable to Prototype Pollution. It allows an attacker to cause a denial of service and may lead to remote code execution.

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 merge
  • Property 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

How to prevent

  1. Freeze the prototype— use Object.freeze (Object.prototype).
  2. Require schema validation of JSON input.
  3. Avoid using unsafe recursive merge functions.
  4. Consider using objects without prototypes (for example, Object.create(null)), breaking the prototype chain and preventing pollution.
  5. As a best practice use Map instead of Object.

For more information on this vulnerability type:

Arteau, Oliver. “JavaScript prototype pollution attack in NodeJS application.” GitHub, 26 May 2018

Remediation

Upgrade getobject to version 1.0.0 or higher.

References

high severity

Arbitrary Code Execution

  • Vulnerable module: grunt
  • Introduced through: grunt@0.4.5

Detailed paths

  • Introduced through: steroids@4.0.10 grunt@0.4.5
    Remediation: Upgrade to grunt@1.3.0.

Overview

grunt is a JavaScript task runner.

Affected versions of this package are vulnerable to Arbitrary Code Execution due to the default usage of the function load() instead of its secure replacement safeLoad() of the package js-yaml inside grunt.file.readYAML.

Remediation

Upgrade grunt to version 1.3.0 or higher.

References

high severity

Arbitrary Code Execution

  • Vulnerable module: handlebars
  • Introduced through: bower@1.3.8

Detailed paths

  • Introduced through: steroids@4.0.10 bower@1.3.8 handlebars@1.3.0
    Remediation: Upgrade to bower@1.7.5.

Overview

handlebars is an extension to the Mustache templating language.

Affected versions of this package are vulnerable to Arbitrary Code Execution. The package's lookup helper doesn't validate templates correctly, allowing attackers to submit templates that execute arbitrary JavaScript in the system.

Remediation

Upgrade handlebars to version 4.5.3, 3.0.8 or higher.

References

high severity

Prototype Pollution

  • Vulnerable module: handlebars
  • Introduced through: bower@1.3.8

Detailed paths

  • Introduced through: steroids@4.0.10 bower@1.3.8 handlebars@1.3.0
    Remediation: Upgrade to bower@1.7.5.

Overview

handlebars is an extension to the Mustache templating language.

Affected versions of this package are vulnerable to Prototype Pollution. Templates may alter an Objects' prototype, thus allowing an attacker to execute arbitrary code on the server.

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 merge
  • Property 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

How to prevent

  1. Freeze the prototype— use Object.freeze (Object.prototype).
  2. Require schema validation of JSON input.
  3. Avoid using unsafe recursive merge functions.
  4. Consider using objects without prototypes (for example, Object.create(null)), breaking the prototype chain and preventing pollution.
  5. As a best practice use Map instead of Object.

For more information on this vulnerability type:

Arteau, Oliver. “JavaScript prototype pollution attack in NodeJS application.” GitHub, 26 May 2018

Remediation

Upgrade handlebars to version 4.0.14, 4.1.2 or higher.

References

high severity

Prototype Pollution

  • Vulnerable module: handlebars
  • Introduced through: bower@1.3.8

Detailed paths

  • Introduced through: steroids@4.0.10 bower@1.3.8 handlebars@1.3.0
    Remediation: Upgrade to bower@1.7.5.

Overview

handlebars is a extension to the Mustache templating language.

Affected versions of this package are vulnerable to Prototype Pollution. Templates may alter an Object's __proto__ and __defineGetter__ properties, which may allow an attacker to execute arbitrary code on the server through crafted payloads.

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 merge
  • Property 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

How to prevent

  1. Freeze the prototype— use Object.freeze (Object.prototype).
  2. Require schema validation of JSON input.
  3. Avoid using unsafe recursive merge functions.
  4. Consider using objects without prototypes (for example, Object.create(null)), breaking the prototype chain and preventing pollution.
  5. As a best practice use Map instead of Object.

For more information on this vulnerability type:

Arteau, Oliver. “JavaScript prototype pollution attack in NodeJS application.” GitHub, 26 May 2018

Remediation

Upgrade handlebars to version 4.3.0, 3.8.0 or higher.

References

high severity

Arbitrary Code Execution

  • Vulnerable module: js-yaml
  • Introduced through: js-yaml@3.0.2, bower@1.3.8 and others

Detailed paths

  • Introduced through: steroids@4.0.10 js-yaml@3.0.2
    Remediation: Upgrade to js-yaml@3.13.1.
  • Introduced through: steroids@4.0.10 bower@1.3.8 insight@0.3.1 configstore@0.2.3 js-yaml@3.0.2
    Remediation: Upgrade to bower@1.3.9.
  • Introduced through: steroids@4.0.10 grunt@0.4.5 js-yaml@2.0.5
    Remediation: Upgrade to grunt@1.0.4.

Overview

js-yaml is a human-friendly data serialization language.

Affected versions of this package are vulnerable to Arbitrary Code Execution. When an object with an executable toString() property used as a map key, it will execute that function. This happens only for load(), which should not be used with untrusted data anyway. safeLoad() is not affected because it can't parse functions.

Remediation

Upgrade js-yaml to version 3.13.1 or higher.

References

high severity

Command Injection

  • Vulnerable module: lodash
  • Introduced through: yeoman-generator@0.17.7, bower@1.3.8 and others

Detailed paths

  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.23.0.
  • Introduced through: steroids@4.0.10 bower@1.3.8 inquirer@0.5.1 lodash@2.4.2
    Remediation: Upgrade to bower@1.7.5.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 cheerio@0.17.0 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.19.0.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 file-utils@0.2.2 lodash@2.4.2
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 findup-sync@0.1.3 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.21.0.
  • Introduced through: steroids@4.0.10 grunt@0.4.5 findup-sync@0.1.3 lodash@2.4.2
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 gruntfile-editor@0.2.0 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.19.0.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 inquirer@0.7.3 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.21.0.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 lodash@2.4.2
  • Introduced through: steroids@4.0.10 grunt@0.4.5 grunt-legacy-log@0.1.3 lodash@2.4.2
    Remediation: Upgrade to grunt@1.0.0.
  • Introduced through: steroids@4.0.10 bower@1.3.8 insight@0.3.1 inquirer@0.4.1 lodash@2.4.2
    Remediation: Upgrade to bower@1.7.5.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 cheerio@0.17.0 lodash@2.4.2
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 file-utils@0.2.2 lodash@2.4.2
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 findup-sync@0.1.3 lodash@2.4.2
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 gruntfile-editor@0.2.0 ast-query@0.2.5 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.19.0.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 gruntfile-editor@0.2.0 lodash@2.4.2
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 inquirer@0.7.3 lodash@2.4.2
  • Introduced through: steroids@4.0.10 grunt@0.4.5 grunt-legacy-log@0.1.3 grunt-legacy-log-utils@0.1.1 lodash@2.4.2
    Remediation: Upgrade to grunt@1.0.3.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 gruntfile-editor@0.2.0 ast-query@0.2.5 lodash@2.4.2
  • Introduced through: steroids@4.0.10 grunt@0.4.5 lodash@0.9.2
    Remediation: Upgrade to grunt@1.0.0.
  • Introduced through: steroids@4.0.10 grunt@0.4.5 grunt-legacy-util@0.2.0 lodash@0.9.2
    Remediation: Upgrade to grunt@1.0.3.
  • Introduced through: steroids@4.0.10 inquirer@0.3.4 lodash@1.2.1
    Remediation: Upgrade to inquirer@0.12.0.
  • Introduced through: steroids@4.0.10 lodash@2.4.1
    Remediation: Upgrade to lodash@4.17.21.

Overview

lodash is a modern JavaScript utility library delivering modularity, performance, & extras.

Affected versions of this package are vulnerable to Command Injection via template.

PoC

var _ = require('lodash');

_.template('', { variable: '){console.log(process.env)}; with(obj' })()

Remediation

Upgrade lodash to version 4.17.21 or higher.

References

high severity

Prototype Pollution

  • Vulnerable module: lodash
  • Introduced through: yeoman-generator@0.17.7, bower@1.3.8 and others

Detailed paths

  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.23.0.
  • Introduced through: steroids@4.0.10 bower@1.3.8 inquirer@0.5.1 lodash@2.4.2
    Remediation: Upgrade to bower@1.7.5.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 cheerio@0.17.0 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.19.0.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 file-utils@0.2.2 lodash@2.4.2
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 findup-sync@0.1.3 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.21.0.
  • Introduced through: steroids@4.0.10 grunt@0.4.5 findup-sync@0.1.3 lodash@2.4.2
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 gruntfile-editor@0.2.0 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.19.0.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 inquirer@0.7.3 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.21.0.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 lodash@2.4.2
  • Introduced through: steroids@4.0.10 grunt@0.4.5 grunt-legacy-log@0.1.3 lodash@2.4.2
    Remediation: Upgrade to grunt@1.0.0.
  • Introduced through: steroids@4.0.10 bower@1.3.8 insight@0.3.1 inquirer@0.4.1 lodash@2.4.2
    Remediation: Upgrade to bower@1.7.5.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 cheerio@0.17.0 lodash@2.4.2
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 file-utils@0.2.2 lodash@2.4.2
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 findup-sync@0.1.3 lodash@2.4.2
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 gruntfile-editor@0.2.0 ast-query@0.2.5 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.19.0.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 gruntfile-editor@0.2.0 lodash@2.4.2
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 inquirer@0.7.3 lodash@2.4.2
  • Introduced through: steroids@4.0.10 grunt@0.4.5 grunt-legacy-log@0.1.3 grunt-legacy-log-utils@0.1.1 lodash@2.4.2
    Remediation: Upgrade to grunt@1.0.3.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 gruntfile-editor@0.2.0 ast-query@0.2.5 lodash@2.4.2
  • Introduced through: steroids@4.0.10 grunt@0.4.5 lodash@0.9.2
    Remediation: Upgrade to grunt@1.0.0.
  • Introduced through: steroids@4.0.10 grunt@0.4.5 grunt-legacy-util@0.2.0 lodash@0.9.2
    Remediation: Upgrade to grunt@1.0.3.
  • Introduced through: steroids@4.0.10 inquirer@0.3.4 lodash@1.2.1
    Remediation: Upgrade to inquirer@0.12.0.
  • Introduced through: steroids@4.0.10 lodash@2.4.1
    Remediation: Upgrade to lodash@4.17.12.

Overview

lodash is a modern JavaScript utility library delivering modularity, performance, & extras.

Affected versions of this package are vulnerable to Prototype Pollution. The function defaultsDeep could be tricked into adding or modifying properties of Object.prototype using a constructor payload.

PoC by Snyk

const mergeFn = require('lodash').defaultsDeep;
const payload = '{"constructor": {"prototype": {"a0": true}}}'

function check() {
    mergeFn({}, JSON.parse(payload));
    if (({})[`a0`] === true) {
        console.log(`Vulnerable to Prototype Pollution via ${payload}`);
    }
  }

check();

For more information, check out our blog post

Details

Prototype Pollution is a vulnerability affecting JavaScript. Prototype Pollution refers to the ability to inject properties into existing JavaScript language construct prototypes, such as objects. JavaScript allows all Object attributes to be altered, including their magical attributes such as _proto_, constructor and prototype. An attacker manipulates these attributes to overwrite, or pollute, a JavaScript application object prototype of the base object by injecting other values. Properties on the Object.prototype are then inherited by all the JavaScript objects through the prototype chain. When that happens, this leads to either denial of service by triggering JavaScript exceptions, or it tampers with the application source code to force the code path that the attacker injects, thereby leading to remote code execution.

There are two main ways in which the pollution of prototypes occurs:

  • Unsafe Object recursive merge
  • Property 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

How to prevent

  1. Freeze the prototype— use Object.freeze (Object.prototype).
  2. Require schema validation of JSON input.
  3. Avoid using unsafe recursive merge functions.
  4. Consider using objects without prototypes (for example, Object.create(null)), breaking the prototype chain and preventing pollution.
  5. As a best practice use Map instead of Object.

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

Prototype Pollution

  • Vulnerable module: lodash
  • Introduced through: yeoman-generator@0.17.7, bower@1.3.8 and others

Detailed paths

  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.23.0.
  • Introduced through: steroids@4.0.10 bower@1.3.8 inquirer@0.5.1 lodash@2.4.2
    Remediation: Upgrade to bower@1.7.5.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 cheerio@0.17.0 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.19.0.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 file-utils@0.2.2 lodash@2.4.2
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 findup-sync@0.1.3 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.21.0.
  • Introduced through: steroids@4.0.10 grunt@0.4.5 findup-sync@0.1.3 lodash@2.4.2
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 gruntfile-editor@0.2.0 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.19.0.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 inquirer@0.7.3 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.21.0.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 lodash@2.4.2
  • Introduced through: steroids@4.0.10 grunt@0.4.5 grunt-legacy-log@0.1.3 lodash@2.4.2
    Remediation: Upgrade to grunt@1.0.0.
  • Introduced through: steroids@4.0.10 bower@1.3.8 insight@0.3.1 inquirer@0.4.1 lodash@2.4.2
    Remediation: Upgrade to bower@1.7.5.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 cheerio@0.17.0 lodash@2.4.2
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 file-utils@0.2.2 lodash@2.4.2
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 findup-sync@0.1.3 lodash@2.4.2
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 gruntfile-editor@0.2.0 ast-query@0.2.5 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.19.0.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 gruntfile-editor@0.2.0 lodash@2.4.2
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 inquirer@0.7.3 lodash@2.4.2
  • Introduced through: steroids@4.0.10 grunt@0.4.5 grunt-legacy-log@0.1.3 grunt-legacy-log-utils@0.1.1 lodash@2.4.2
    Remediation: Upgrade to grunt@1.0.3.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 gruntfile-editor@0.2.0 ast-query@0.2.5 lodash@2.4.2
  • Introduced through: steroids@4.0.10 grunt@0.4.5 lodash@0.9.2
    Remediation: Upgrade to grunt@1.0.0.
  • Introduced through: steroids@4.0.10 grunt@0.4.5 grunt-legacy-util@0.2.0 lodash@0.9.2
    Remediation: Upgrade to grunt@1.0.3.
  • Introduced through: steroids@4.0.10 inquirer@0.3.4 lodash@1.2.1
    Remediation: Upgrade to inquirer@0.12.0.
  • Introduced through: steroids@4.0.10 lodash@2.4.1
    Remediation: Upgrade to lodash@4.17.17.

Overview

lodash is a modern JavaScript utility library delivering modularity, performance, & extras.

Affected versions of this package are vulnerable to Prototype Pollution via the setWith and set functions.

PoC by awarau

  • Create a JS file with this contents:
    lod = require('lodash')
    lod.setWith({}, "__proto__[test]", "123")
    lod.set({}, "__proto__[test2]", "456")
    console.log(Object.prototype)
    
  • Execute it with node
  • Observe that test and test2 is now in the 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 merge
  • Property 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

How to prevent

  1. Freeze the prototype— use Object.freeze (Object.prototype).
  2. Require schema validation of JSON input.
  3. Avoid using unsafe recursive merge functions.
  4. Consider using objects without prototypes (for example, Object.create(null)), breaking the prototype chain and preventing pollution.
  5. As a best practice use Map instead of Object.

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

Prototype Pollution

  • Vulnerable module: lodash
  • Introduced through: yeoman-generator@0.17.7, bower@1.3.8 and others

Detailed paths

  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.23.0.
  • Introduced through: steroids@4.0.10 bower@1.3.8 inquirer@0.5.1 lodash@2.4.2
    Remediation: Upgrade to bower@1.7.5.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 cheerio@0.17.0 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.19.0.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 file-utils@0.2.2 lodash@2.4.2
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 findup-sync@0.1.3 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.21.0.
  • Introduced through: steroids@4.0.10 grunt@0.4.5 findup-sync@0.1.3 lodash@2.4.2
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 gruntfile-editor@0.2.0 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.19.0.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 inquirer@0.7.3 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.21.0.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 lodash@2.4.2
  • Introduced through: steroids@4.0.10 grunt@0.4.5 grunt-legacy-log@0.1.3 lodash@2.4.2
    Remediation: Upgrade to grunt@1.0.0.
  • Introduced through: steroids@4.0.10 bower@1.3.8 insight@0.3.1 inquirer@0.4.1 lodash@2.4.2
    Remediation: Upgrade to bower@1.7.5.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 cheerio@0.17.0 lodash@2.4.2
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 file-utils@0.2.2 lodash@2.4.2
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 findup-sync@0.1.3 lodash@2.4.2
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 gruntfile-editor@0.2.0 ast-query@0.2.5 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.19.0.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 gruntfile-editor@0.2.0 lodash@2.4.2
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 inquirer@0.7.3 lodash@2.4.2
  • Introduced through: steroids@4.0.10 grunt@0.4.5 grunt-legacy-log@0.1.3 grunt-legacy-log-utils@0.1.1 lodash@2.4.2
    Remediation: Upgrade to grunt@1.0.3.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 gruntfile-editor@0.2.0 ast-query@0.2.5 lodash@2.4.2
  • Introduced through: steroids@4.0.10 grunt@0.4.5 lodash@0.9.2
    Remediation: Upgrade to grunt@1.0.0.
  • Introduced through: steroids@4.0.10 grunt@0.4.5 grunt-legacy-util@0.2.0 lodash@0.9.2
    Remediation: Upgrade to grunt@1.0.3.
  • Introduced through: steroids@4.0.10 inquirer@0.3.4 lodash@1.2.1
    Remediation: Upgrade to inquirer@0.12.0.
  • Introduced through: steroids@4.0.10 lodash@2.4.1
    Remediation: Upgrade to lodash@4.17.11.

Overview

lodash is a modern JavaScript utility library delivering modularity, performance, & extras.

Affected versions of this package are vulnerable to Prototype Pollution. The functions merge, mergeWith, and defaultsDeep could be tricked into adding or modifying properties of Object.prototype. This is due to an incomplete fix to CVE-2018-3721.

Details

Prototype Pollution is a vulnerability affecting JavaScript. Prototype Pollution refers to the ability to inject properties into existing JavaScript language construct prototypes, such as objects. JavaScript allows all Object attributes to be altered, including their magical attributes such as _proto_, constructor and prototype. An attacker manipulates these attributes to overwrite, or pollute, a JavaScript application object prototype of the base object by injecting other values. Properties on the Object.prototype are then inherited by all the JavaScript objects through the prototype chain. When that happens, this leads to either denial of service by triggering JavaScript exceptions, or it tampers with the application source code to force the code path that the attacker injects, thereby leading to remote code execution.

There are two main ways in which the pollution of prototypes occurs:

  • Unsafe Object recursive merge
  • Property 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

How to prevent

  1. Freeze the prototype— use Object.freeze (Object.prototype).
  2. Require schema validation of JSON input.
  3. Avoid using unsafe recursive merge functions.
  4. Consider using objects without prototypes (for example, Object.create(null)), breaking the prototype chain and preventing pollution.
  5. As a best practice use Map instead of Object.

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

Regular Expression Denial of Service (ReDoS)

  • Vulnerable module: minimatch
  • Introduced through: bower@1.3.8, yeoman-generator@0.17.7 and others

Detailed paths

  • Introduced through: steroids@4.0.10 bower@1.3.8 fstream-ignore@0.0.10 minimatch@0.3.0
    Remediation: Upgrade to bower@1.3.10.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 findup-sync@0.1.3 glob@3.2.11 minimatch@0.3.0
    Remediation: Upgrade to yeoman-generator@0.21.0.
  • Introduced through: steroids@4.0.10 grunt@0.4.5 findup-sync@0.1.3 glob@3.2.11 minimatch@0.3.0
    Remediation: Upgrade to grunt@1.0.0.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 findup-sync@0.1.3 glob@3.2.11 minimatch@0.3.0
  • Introduced through: steroids@4.0.10 npm@2.1.7 minimatch@1.0.0
    Remediation: Upgrade to npm@2.14.9.
  • Introduced through: steroids@4.0.10 bower@1.3.8 glob@4.0.6 minimatch@1.0.0
    Remediation: Upgrade to bower@1.7.5.
  • Introduced through: steroids@4.0.10 npm@2.1.7 glob@4.0.6 minimatch@1.0.0
    Remediation: Upgrade to npm@2.7.4.
  • Introduced through: steroids@4.0.10 npm@2.1.7 node-gyp@1.0.3 minimatch@1.0.0
    Remediation: Upgrade to npm@2.15.9.
  • Introduced through: steroids@4.0.10 grunt@0.4.5 minimatch@0.2.14
    Remediation: Upgrade to grunt@1.0.0.
  • Introduced through: steroids@4.0.10 chokidar@0.10.3 readdirp@1.1.0 minimatch@0.2.14
    Remediation: Upgrade to chokidar@1.1.0.
  • Introduced through: steroids@4.0.10 grunt@0.4.5 glob@3.1.21 minimatch@0.2.14
    Remediation: Upgrade to grunt@1.0.0.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 glob@4.5.3 minimatch@2.0.10
    Remediation: Upgrade to yeoman-generator@0.19.0.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 file-utils@0.2.2 minimatch@2.0.10
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 file-utils@0.2.2 glob@4.5.3 minimatch@2.0.10
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 glob@4.5.3 minimatch@2.0.10
  • Introduced through: steroids@4.0.10 npm@2.1.7 init-package-json@1.1.3 glob@4.5.3 minimatch@2.0.10
    Remediation: Upgrade to npm@2.7.0.
  • Introduced through: steroids@4.0.10 npm@2.1.7 node-gyp@1.0.3 glob@4.5.3 minimatch@2.0.10
    Remediation: Upgrade to npm@2.15.9.
  • Introduced through: steroids@4.0.10 npm@2.1.7 read-package-json@1.2.7 glob@4.5.3 minimatch@2.0.10
    Remediation: Upgrade to npm@2.6.0.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 file-utils@0.2.2 minimatch@2.0.10
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 file-utils@0.2.2 findup-sync@0.2.1 glob@4.3.5 minimatch@2.0.10
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 file-utils@0.2.2 glob@4.5.3 minimatch@2.0.10
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 file-utils@0.2.2 findup-sync@0.2.1 glob@4.3.5 minimatch@2.0.10

Overview

minimatch is a minimal matching utility.

Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS) via complicated and illegal regexes.

Details

Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.

The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.

Let’s take the following regular expression as an example:

regex = /A(B|C+)+D/

This regular expression accomplishes the following:

  • A The string must start with the letter 'A'
  • (B|C+)+ The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the + matches one or more times). The + at the end of this section states that we can look for one or more matches of this section.
  • D Finally, we ensure this section of the string ends with a 'D'

The expression would match inputs such as ABBD, ABCCCCD, ABCBCCCD and ACCCCCD

It most cases, it doesn't take very long for a regex engine to find a match:

$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total

$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total

The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.

Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.

Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:

  1. CCC
  2. CC+C
  3. C+CC
  4. C+C+C.

The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.

From there, the number of steps the engine must use to validate a string just continues to grow.

String Number of C's Number of steps
ACCCX 3 38
ACCCCX 4 71
ACCCCCX 5 136
ACCCCCCCCCCCCCCX 14 65,553

By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.

Remediation

Upgrade minimatch to version 3.0.2 or higher.

References

high severity

Regular Expression Denial of Service (ReDoS)

  • Vulnerable module: minimatch
  • Introduced through: bower@1.3.8, yeoman-generator@0.17.7 and others

Detailed paths

  • Introduced through: steroids@4.0.10 bower@1.3.8 fstream-ignore@0.0.10 minimatch@0.3.0
    Remediation: Upgrade to bower@1.3.10.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 findup-sync@0.1.3 glob@3.2.11 minimatch@0.3.0
    Remediation: Upgrade to yeoman-generator@0.21.0.
  • Introduced through: steroids@4.0.10 grunt@0.4.5 findup-sync@0.1.3 glob@3.2.11 minimatch@0.3.0
    Remediation: Upgrade to grunt@1.0.0.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 findup-sync@0.1.3 glob@3.2.11 minimatch@0.3.0
    Remediation: Open PR to patch minimatch@0.3.0.
  • Introduced through: steroids@4.0.10 npm@2.1.7 minimatch@1.0.0
    Remediation: Upgrade to npm@2.14.9.
  • Introduced through: steroids@4.0.10 bower@1.3.8 glob@4.0.6 minimatch@1.0.0
    Remediation: Upgrade to bower@1.7.5.
  • Introduced through: steroids@4.0.10 npm@2.1.7 glob@4.0.6 minimatch@1.0.0
    Remediation: Upgrade to npm@2.7.4.
  • Introduced through: steroids@4.0.10 npm@2.1.7 node-gyp@1.0.3 minimatch@1.0.0
    Remediation: Upgrade to npm@2.15.9.
  • Introduced through: steroids@4.0.10 grunt@0.4.5 minimatch@0.2.14
    Remediation: Upgrade to grunt@1.0.0.
  • Introduced through: steroids@4.0.10 chokidar@0.10.3 readdirp@1.1.0 minimatch@0.2.14
    Remediation: Upgrade to chokidar@1.1.0.
  • Introduced through: steroids@4.0.10 grunt@0.4.5 glob@3.1.21 minimatch@0.2.14
    Remediation: Upgrade to grunt@1.0.0.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 glob@4.5.3 minimatch@2.0.10
    Remediation: Upgrade to yeoman-generator@0.19.0.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 file-utils@0.2.2 minimatch@2.0.10
    Remediation: Open PR to patch minimatch@2.0.10.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 file-utils@0.2.2 glob@4.5.3 minimatch@2.0.10
    Remediation: Open PR to patch minimatch@2.0.10.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 glob@4.5.3 minimatch@2.0.10
    Remediation: Open PR to patch minimatch@2.0.10.
  • Introduced through: steroids@4.0.10 npm@2.1.7 init-package-json@1.1.3 glob@4.5.3 minimatch@2.0.10
    Remediation: Upgrade to npm@2.7.0.
  • Introduced through: steroids@4.0.10 npm@2.1.7 node-gyp@1.0.3 glob@4.5.3 minimatch@2.0.10
    Remediation: Upgrade to npm@2.15.9.
  • Introduced through: steroids@4.0.10 npm@2.1.7 read-package-json@1.2.7 glob@4.5.3 minimatch@2.0.10
    Remediation: Upgrade to npm@2.6.0.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 file-utils@0.2.2 minimatch@2.0.10
    Remediation: Open PR to patch minimatch@2.0.10.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 file-utils@0.2.2 findup-sync@0.2.1 glob@4.3.5 minimatch@2.0.10
    Remediation: Open PR to patch minimatch@2.0.10.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 file-utils@0.2.2 glob@4.5.3 minimatch@2.0.10
    Remediation: Open PR to patch minimatch@2.0.10.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 file-utils@0.2.2 findup-sync@0.2.1 glob@4.3.5 minimatch@2.0.10
    Remediation: Open PR to patch minimatch@2.0.10.

Overview

minimatch is a minimal matching utility.

Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS).

Details

Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.

The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.

Let’s take the following regular expression as an example:

regex = /A(B|C+)+D/

This regular expression accomplishes the following:

  • A The string must start with the letter 'A'
  • (B|C+)+ The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the + matches one or more times). The + at the end of this section states that we can look for one or more matches of this section.
  • D Finally, we ensure this section of the string ends with a 'D'

The expression would match inputs such as ABBD, ABCCCCD, ABCBCCCD and ACCCCCD

It most cases, it doesn't take very long for a regex engine to find a match:

$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total

$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total

The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.

Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.

Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:

  1. CCC
  2. CC+C
  3. C+CC
  4. C+C+C.

The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.

From there, the number of steps the engine must use to validate a string just continues to grow.

String Number of C's Number of steps
ACCCX 3 38
ACCCCX 4 71
ACCCCCX 5 136
ACCCCCCCCCCCCCCX 14 65,553

By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.

Remediation

Upgrade minimatch to version 3.0.2 or higher.

References

high severity

Prototype Pollution

  • Vulnerable module: mout
  • Introduced through: bower@1.3.8

Detailed paths

  • Introduced through: steroids@4.0.10 bower@1.3.8 mout@0.9.1
  • Introduced through: steroids@4.0.10 bower@1.3.8 bower-config@0.5.3 mout@0.9.1
  • Introduced through: steroids@4.0.10 bower@1.3.8 bower-registry-client@0.2.4 bower-config@0.5.3 mout@0.9.1

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 a Prototype Pollution.

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 merge
  • Property 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

How to prevent

  1. Freeze the prototype— use Object.freeze (Object.prototype).
  2. Require schema validation of JSON input.
  3. Avoid using unsafe recursive merge functions.
  4. Consider using objects without prototypes (for example, Object.create(null)), breaking the prototype chain and preventing pollution.
  5. As a best practice use Map instead of Object.

For more information on this vulnerability type:

Arteau, Oliver. “JavaScript prototype pollution attack in NodeJS application.” GitHub, 26 May 2018

Remediation

There is no fixed version for mout.

References

high severity

Regular Expression Denial of Service (ReDoS)

  • Vulnerable module: negotiator
  • Introduced through: express@4.8.8

Detailed paths

  • Introduced through: steroids@4.0.10 express@4.8.8 accepts@1.0.7 negotiator@0.4.7
    Remediation: Upgrade to express@4.14.0.

Overview

negotiator is an HTTP content negotiator for Node.js.

Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS) when parsing Accept-Language http header.

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:

  1. CCC
  2. CC+C
  3. C+CC
  4. 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 negotiator to version 0.6.1 or higher.

References

high severity

Arbitrary File Overwrite

  • Vulnerable module: npm
  • Introduced through: npm@2.1.7

Detailed paths

  • Introduced through: steroids@4.0.10 npm@2.1.7
    Remediation: Upgrade to npm@6.13.4.

Overview

npm is a package manager for JavaScript.

Affected versions of this package are vulnerable to Arbitrary File Overwrite. It fails to prevent existing globally-installed binaries to be overwritten by other package installations. For example, if a package was installed globally and created a serve binary, any subsequent installs of packages that also create a serve binary would overwrite the first binary. This only affects files in /usr/local/bin.

For npm, this behaviour is still allowed in local installations and also through install scripts. This vulnerability bypasses a user using the --ignore-scripts install option.

Details

A Directory Traversal attack (also known as path traversal) aims to access files and directories that are stored outside the intended folder. By manipulating files with "dot-dot-slash (../)" sequences and its variations, or by using absolute file paths, it may be possible to access arbitrary files and directories stored on file system, including application source code, configuration, and other critical system files.

Directory Traversal vulnerabilities can be generally divided into two types:

  • Information Disclosure: Allows the attacker to gain information about the folder structure or read the contents of sensitive files on the system.

st is a module for serving static files on web pages, and contains a vulnerability of this type. In our example, we will serve files from the public route.

If an attacker requests the following URL from our server, it will in turn leak the sensitive private key of the root user.

curl http://localhost:8080/public/%2e%2e/%2e%2e/%2e%2e/%2e%2e/%2e%2e/root/.ssh/id_rsa

Note %2e is the URL encoded version of . (dot).

  • Writing arbitrary files: Allows the attacker to create or replace existing files. This type of vulnerability is also known as Zip-Slip.

One way to achieve this is by using a malicious zip archive that holds path traversal filenames. When each filename in the zip archive gets concatenated to the target extraction folder, without validation, the final path ends up outside of the target folder. If an executable or a configuration file is overwritten with a file containing malicious code, the problem can turn into an arbitrary code execution issue quite easily.

The following is an example of a zip archive with one benign file and one malicious file. Extracting the malicious file will result in traversing out of the target folder, ending up in /root/.ssh/ overwriting the authorized_keys file:

2018-04-15 22:04:29 .....           19           19  good.txt
2018-04-15 22:04:42 .....           20           20  ../../../../../../root/.ssh/authorized_keys

Remediation

Upgrade npm to version 6.13.4 or higher.

References

high severity

Arbitrary File Write

  • Vulnerable module: npm
  • Introduced through: npm@2.1.7

Detailed paths

  • Introduced through: steroids@4.0.10 npm@2.1.7
    Remediation: Upgrade to npm@6.13.3.

Overview

npm is a package manager for JavaScript.

Affected versions of this package are vulnerable to Arbitrary File Write. It fails to prevent access to folders outside of the intended node_modules folder through the bin field.

For npm, a properly constructed entry in the package.json bin field would allow a package publisher to modify and/or gain access to arbitrary files on a user’s system when the package is installed. This behaviour is possible through install scripts. This vulnerability bypasses a user using the --ignore-scripts install option.

Details

A Directory Traversal attack (also known as path traversal) aims to access files and directories that are stored outside the intended folder. By manipulating files with "dot-dot-slash (../)" sequences and its variations, or by using absolute file paths, it may be possible to access arbitrary files and directories stored on file system, including application source code, configuration, and other critical system files.

Directory Traversal vulnerabilities can be generally divided into two types:

  • Information Disclosure: Allows the attacker to gain information about the folder structure or read the contents of sensitive files on the system.

st is a module for serving static files on web pages, and contains a vulnerability of this type. In our example, we will serve files from the public route.

If an attacker requests the following URL from our server, it will in turn leak the sensitive private key of the root user.

curl http://localhost:8080/public/%2e%2e/%2e%2e/%2e%2e/%2e%2e/%2e%2e/root/.ssh/id_rsa

Note %2e is the URL encoded version of . (dot).

  • Writing arbitrary files: Allows the attacker to create or replace existing files. This type of vulnerability is also known as Zip-Slip.

One way to achieve this is by using a malicious zip archive that holds path traversal filenames. When each filename in the zip archive gets concatenated to the target extraction folder, without validation, the final path ends up outside of the target folder. If an executable or a configuration file is overwritten with a file containing malicious code, the problem can turn into an arbitrary code execution issue quite easily.

The following is an example of a zip archive with one benign file and one malicious file. Extracting the malicious file will result in traversing out of the target folder, ending up in /root/.ssh/ overwriting the authorized_keys file:

2018-04-15 22:04:29 .....           19           19  good.txt
2018-04-15 22:04:42 .....           20           20  ../../../../../../root/.ssh/authorized_keys

Remediation

Upgrade npm to version 6.13.3 or higher.

References

high severity

Regular Expression Denial of Service (ReDoS)

  • Vulnerable module: npm-user-validate
  • Introduced through: npm@2.1.7

Detailed paths

  • Introduced through: steroids@4.0.10 npm@2.1.7 npm-user-validate@0.1.5
    Remediation: Upgrade to npm@5.0.1.

Overview

npm-user-validate is an User validations for npm

Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS). The regex that validates user emails took exponentially longer to process long input strings beginning with @ 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:

  1. CCC
  2. CC+C
  3. C+CC
  4. 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 npm-user-validate to version 1.0.1 or higher.

References

high severity

Arbitrary Command Injection

  • Vulnerable module: open
  • Introduced through: open@0.0.4

Detailed paths

  • Introduced through: steroids@4.0.10 open@0.0.4
    Remediation: Upgrade to open@6.0.0.

Overview

open is a cross platform package that opens stuff like URLs, files, executables.

Affected versions of this package are vulnerable to Arbitrary Command Injection. Urls are not properly escaped before concatenating them into the command that is opened using exec().

Note: Upgrading open to the last version will prevent this vulnerability but is also likely to have unwanted effects since it now has a very different API.

Remediation

Upgrade open to version 6.0.0 or higher.

References

high severity

Denial of Service (DoS)

  • Vulnerable module: qs
  • Introduced through: request@2.27.0, restler@3.2.2 and others

Detailed paths

  • Introduced through: steroids@4.0.10 request@2.27.0 qs@0.6.6
    Remediation: Upgrade to steroids@4.0.12.
  • Introduced through: steroids@4.0.10 restler@3.2.2 qs@0.6.6
    Remediation: Upgrade to restler@3.3.0.
  • Introduced through: steroids@4.0.10 bower@1.3.8 request@2.36.0 qs@0.6.6
    Remediation: Upgrade to bower@1.3.10.
  • Introduced through: steroids@4.0.10 bower@1.3.8 insight@0.3.1 request@2.27.0 qs@0.6.6
    Remediation: Upgrade to bower@1.3.9.
  • Introduced through: steroids@4.0.10 winston@0.7.3 request@2.16.6 qs@0.5.6
    Remediation: Upgrade to winston@0.8.0.

Overview

qs is a querystring parser that supports nesting and arrays, with a depth limit.

Affected versions of this package are vulnerable to Denial of Service (DoS). During parsing, the qs module may create a sparse area (an array where no elements are filled), and grow that array to the necessary size based on the indices used on it. An attacker can specify a high index value in a query string, thus making the server allocate a respectively big array. Truly large values can cause the server to run out of memory and cause it to crash - thus enabling a Denial-of-Service attack.

Remediation

Upgrade qs to version 1.0.0 or higher.

Details

Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its intended and legitimate users.

Unlike other vulnerabilities, DoS attacks usually do not aim at breaching security. Rather, they are focused on making websites and services unavailable to genuine users resulting in downtime.

One popular Denial of Service vulnerability is DDoS (a Distributed Denial of Service), an attack that attempts to clog network pipes to the system by generating a large volume of traffic from many machines.

When it comes to open source libraries, DoS vulnerabilities allow attackers to trigger such a crash or crippling of the service by using a flaw either in the application code or from the use of open source libraries.

Two common types of DoS vulnerabilities:

  • High CPU/Memory Consumption- An attacker sending crafted requests that could cause the system to take a disproportionate amount of time to process. For example, commons-fileupload:commons-fileupload.

  • Crash - An attacker sending crafted requests that could cause the system to crash. For Example, npm ws package

References

high severity

Prototype Override Protection Bypass

  • Vulnerable module: qs
  • Introduced through: body-parser@1.8.1, npm@2.1.7 and others

Detailed paths

  • Introduced through: steroids@4.0.10 body-parser@1.8.1 qs@2.2.3
    Remediation: Upgrade to body-parser@1.17.1.
  • Introduced through: steroids@4.0.10 npm@2.1.7 request@2.47.0 qs@2.3.3
    Remediation: Upgrade to npm@2.14.18.
  • Introduced through: steroids@4.0.10 bower@1.3.8 bower-registry-client@0.2.4 request@2.51.0 qs@2.3.3
    Remediation: Upgrade to bower@1.6.2.
  • Introduced through: steroids@4.0.10 request@2.27.0 qs@0.6.6
    Remediation: Upgrade to request@2.68.0.
  • Introduced through: steroids@4.0.10 restler@3.2.2 qs@0.6.6
  • Introduced through: steroids@4.0.10 bower@1.3.8 request@2.36.0 qs@0.6.6
    Remediation: Upgrade to bower@1.7.5.
  • Introduced through: steroids@4.0.10 bower@1.3.8 insight@0.3.1 request@2.27.0 qs@0.6.6
    Remediation: Upgrade to bower@1.3.9.
  • Introduced through: steroids@4.0.10 express@4.8.8 qs@2.2.2
    Remediation: Upgrade to express@4.15.2.
  • Introduced through: steroids@4.0.10 winston@0.7.3 request@2.16.6 qs@0.5.6
    Remediation: Upgrade to winston@0.8.0.

Overview

qs is a querystring parser that supports nesting and arrays, with a depth limit.

Affected versions of this package are vulnerable to Prototype Override Protection Bypass. By default qs protects against attacks that attempt to overwrite an object's existing prototype properties, such as toString(), hasOwnProperty(),etc.

From qs documentation:

By default parameters that would overwrite properties on the object prototype are ignored, if you wish to keep the data from those fields either use plainObjects as mentioned above, or set allowPrototypes to true which will allow user input to overwrite those properties. WARNING It is generally a bad idea to enable this option as it can cause problems when attempting to use the properties that have been overwritten. Always be careful with this option.

Overwriting these properties can impact application logic, potentially allowing attackers to work around security controls, modify data, make the application unstable and more.

In versions of the package affected by this vulnerability, it is possible to circumvent this protection and overwrite prototype properties and functions by prefixing the name of the parameter with [ or ]. e.g. qs.parse("]=toString") will return {toString = true}, as a result, calling toString() on the object will throw an exception.

Example:

qs.parse('toString=foo', { allowPrototypes: false })
// {}

qs.parse("]=toString", { allowPrototypes: false })
// {toString = true} <== prototype overwritten

For more information, you can check out our blog.

Disclosure Timeline

  • February 13th, 2017 - Reported the issue to package owner.
  • February 13th, 2017 - Issue acknowledged by package owner.
  • February 16th, 2017 - Partial fix released in versions 6.0.3, 6.1.1, 6.2.2, 6.3.1.
  • March 6th, 2017 - Final fix released in versions 6.4.0,6.3.2, 6.2.3, 6.1.2 and 6.0.4

    Remediation

    Upgrade qs to version 6.0.4, 6.1.2, 6.2.3, 6.3.2 or higher.

    References

  • GitHub Commit
  • GitHub Issue

high severity

Command Injection

  • Vulnerable module: shell-quote
  • Introduced through: bower@1.3.8

Detailed paths

  • Introduced through: steroids@4.0.10 bower@1.3.8 shell-quote@1.4.3
    Remediation: Upgrade to bower@1.4.0.

Overview

shell-quote is a package used to quote and parse shell commands.

Affected versions of this package are vulnerable to Command Injection. The quote function does not properly escape the following special characters <, >, ;, {, } , and as a result can be used by an attacker to inject malicious shell commands or leak sensitive information.

Proof of Concept

Consider the following poc.js application

var quote = require('shell-quote').quote;
var exec = require('child_process').exec;

var userInput = process.argv[2];

var safeCommand = quote(['echo', userInput]);

exec(safeCommand, function (err, stdout, stderr) {
  console.log(stdout);
});

Running the following command will not only print the character a as expected, but will also run the another command, i.e touch malicious.sh

$ node poc.js 'a;{touch,malicious.sh}'

Remediation

Upgrade shell-quote to version 1.6.1 or higher.

References

high severity

Resources Downloaded over Insecure Protocol

  • Vulnerable module: steroids
  • Introduced through: steroids@4.0.10

Detailed paths

  • Introduced through: steroids@4.0.10

Overview

steroids is an AppGyver Steroids Command Line Interface. Affected versions of the package are vulnerable to Man in the Middle (MitM) attacks due to downloading resources over an insecure protocol.

Remediation

There is no fix version for steroids.

high severity

Arbitrary File Overwrite

  • Vulnerable module: tar
  • Introduced through: bower@1.3.8, npm@2.1.7 and others

Detailed paths

  • Introduced through: steroids@4.0.10 bower@1.3.8 tar@0.1.20
    Remediation: Upgrade to bower@1.3.10.
  • Introduced through: steroids@4.0.10 npm@2.1.7 tar@1.0.3
    Remediation: Upgrade to npm@5.6.0.
  • Introduced through: steroids@4.0.10 npm@2.1.7 node-gyp@1.0.3 tar@1.0.3
    Remediation: Upgrade to npm@5.6.0.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-tar@1.0.3 tar@1.0.3
    Remediation: Upgrade to yeoman-generator@0.24.1.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-tarbz2@1.0.2 tar@1.0.3
    Remediation: Upgrade to yeoman-generator@0.24.1.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-targz@1.0.3 tar@1.0.3
    Remediation: Upgrade to yeoman-generator@0.24.1.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-tar@1.0.3 tar@1.0.3
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-tarbz2@1.0.2 tar@1.0.3
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-targz@1.0.3 tar@1.0.3

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

Arbitrary File Overwrite

  • Vulnerable module: tar
  • Introduced through: bower@1.3.8, npm@2.1.7 and others

Detailed paths

  • Introduced through: steroids@4.0.10 bower@1.3.8 tar@0.1.20
    Remediation: Upgrade to bower@1.3.10.
  • Introduced through: steroids@4.0.10 npm@2.1.7 tar@1.0.3
    Remediation: Upgrade to npm@5.6.0.
  • Introduced through: steroids@4.0.10 npm@2.1.7 node-gyp@1.0.3 tar@1.0.3
    Remediation: Upgrade to npm@5.6.0.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-tar@1.0.3 tar@1.0.3
    Remediation: Upgrade to yeoman-generator@0.24.1.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-tarbz2@1.0.2 tar@1.0.3
    Remediation: Upgrade to yeoman-generator@0.24.1.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-targz@1.0.3 tar@1.0.3
    Remediation: Upgrade to yeoman-generator@0.24.1.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-tar@1.0.3 tar@1.0.3
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-tarbz2@1.0.2 tar@1.0.3
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-targz@1.0.3 tar@1.0.3

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

Arbitrary File Overwrite

  • Vulnerable module: tar
  • Introduced through: bower@1.3.8, npm@2.1.7 and others

Detailed paths

  • Introduced through: steroids@4.0.10 bower@1.3.8 tar@0.1.20
    Remediation: Upgrade to bower@1.3.10.
  • Introduced through: steroids@4.0.10 npm@2.1.7 tar@1.0.3
    Remediation: Upgrade to npm@2.14.2.
  • Introduced through: steroids@4.0.10 npm@2.1.7 node-gyp@1.0.3 tar@1.0.3
    Remediation: Upgrade to npm@2.14.13.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-tar@1.0.3 tar@1.0.3
    Remediation: Upgrade to yeoman-generator@0.24.1.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-tarbz2@1.0.2 tar@1.0.3
    Remediation: Upgrade to yeoman-generator@0.24.1.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-targz@1.0.3 tar@1.0.3
    Remediation: Upgrade to yeoman-generator@0.24.1.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-tar@1.0.3 tar@1.0.3
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-tarbz2@1.0.2 tar@1.0.3
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-targz@1.0.3 tar@1.0.3

Overview

tar is a full-featured Tar for Node.js.

Affected versions of this package are vulnerable to Arbitrary File Overwrite. Extracting tarballs containing a hard-link to a file that already exists in the system, and a file that matches the hard-link may overwrite system's files with the contents of the extracted file.

Remediation

Upgrade tar to version 2.2.2, 4.4.2 or higher.

References

high severity

Arbitrary File Write

  • Vulnerable module: tar
  • Introduced through: bower@1.3.8, npm@2.1.7 and others

Detailed paths

  • Introduced through: steroids@4.0.10 bower@1.3.8 tar@0.1.20
    Remediation: Upgrade to bower@1.3.10.
  • Introduced through: steroids@4.0.10 npm@2.1.7 tar@1.0.3
    Remediation: Upgrade to npm@5.6.0.
  • Introduced through: steroids@4.0.10 npm@2.1.7 node-gyp@1.0.3 tar@1.0.3
    Remediation: Upgrade to npm@5.6.0.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-tar@1.0.3 tar@1.0.3
    Remediation: Upgrade to yeoman-generator@0.24.1.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-tarbz2@1.0.2 tar@1.0.3
    Remediation: Upgrade to yeoman-generator@0.24.1.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-targz@1.0.3 tar@1.0.3
    Remediation: Upgrade to yeoman-generator@0.24.1.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-tar@1.0.3 tar@1.0.3
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-tarbz2@1.0.2 tar@1.0.3
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-targz@1.0.3 tar@1.0.3

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

Arbitrary File Write

  • Vulnerable module: tar
  • Introduced through: bower@1.3.8, npm@2.1.7 and others

Detailed paths

  • Introduced through: steroids@4.0.10 bower@1.3.8 tar@0.1.20
    Remediation: Upgrade to bower@1.3.10.
  • Introduced through: steroids@4.0.10 npm@2.1.7 tar@1.0.3
    Remediation: Upgrade to npm@5.6.0.
  • Introduced through: steroids@4.0.10 npm@2.1.7 node-gyp@1.0.3 tar@1.0.3
    Remediation: Upgrade to npm@5.6.0.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-tar@1.0.3 tar@1.0.3
    Remediation: Upgrade to yeoman-generator@0.24.1.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-tarbz2@1.0.2 tar@1.0.3
    Remediation: Upgrade to yeoman-generator@0.24.1.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-targz@1.0.3 tar@1.0.3
    Remediation: Upgrade to yeoman-generator@0.24.1.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-tar@1.0.3 tar@1.0.3
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-tarbz2@1.0.2 tar@1.0.3
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-targz@1.0.3 tar@1.0.3

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

Arbitrary File Write

  • Vulnerable module: tar
  • Introduced through: bower@1.3.8, npm@2.1.7 and others

Detailed paths

  • Introduced through: steroids@4.0.10 bower@1.3.8 tar@0.1.20
    Remediation: Upgrade to bower@1.3.10.
  • Introduced through: steroids@4.0.10 npm@2.1.7 tar@1.0.3
    Remediation: Upgrade to npm@5.6.0.
  • Introduced through: steroids@4.0.10 npm@2.1.7 node-gyp@1.0.3 tar@1.0.3
    Remediation: Upgrade to npm@5.6.0.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-tar@1.0.3 tar@1.0.3
    Remediation: Upgrade to yeoman-generator@0.24.1.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-tarbz2@1.0.2 tar@1.0.3
    Remediation: Upgrade to yeoman-generator@0.24.1.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-targz@1.0.3 tar@1.0.3
    Remediation: Upgrade to yeoman-generator@0.24.1.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-tar@1.0.3 tar@1.0.3
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-tarbz2@1.0.2 tar@1.0.3
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-targz@1.0.3 tar@1.0.3

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

Symlink File Overwrite

  • Vulnerable module: tar
  • Introduced through: bower@1.3.8, npm@2.1.7 and others

Detailed paths

  • Introduced through: steroids@4.0.10 bower@1.3.8 tar@0.1.20
    Remediation: Upgrade to bower@1.3.10.
  • Introduced through: steroids@4.0.10 npm@2.1.7 tar@1.0.3
    Remediation: Upgrade to npm@2.7.5.
  • Introduced through: steroids@4.0.10 npm@2.1.7 node-gyp@1.0.3 tar@1.0.3
    Remediation: Upgrade to npm@2.14.13.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-tar@1.0.3 tar@1.0.3
    Remediation: Upgrade to yeoman-generator@0.24.1.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-tarbz2@1.0.2 tar@1.0.3
    Remediation: Upgrade to yeoman-generator@0.24.1.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-targz@1.0.3 tar@1.0.3
    Remediation: Upgrade to yeoman-generator@0.24.1.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-tar@1.0.3 tar@1.0.3
    Remediation: Open PR to patch tar@1.0.3.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-tarbz2@1.0.2 tar@1.0.3
    Remediation: Open PR to patch tar@1.0.3.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-targz@1.0.3 tar@1.0.3
    Remediation: Open PR to patch tar@1.0.3.

Overview

tar is a full-featured Tar for Node.js.

Affected versions of this package are vulnerable to Symlink File Overwrite. It does not properly normalize symbolic links pointing to targets outside the extraction root. As a result, packages may hold symbolic links to parent and sibling directories and overwrite those files when the package is extracted.

Remediation

Upgrade tar to version 2.0.0 or higher.

References

high severity

Improper minification of non-boolean comparisons

  • Vulnerable module: uglify-js
  • Introduced through: bower@1.3.8

Detailed paths

  • Introduced through: steroids@4.0.10 bower@1.3.8 handlebars@1.3.0 uglify-js@2.3.6
    Remediation: Upgrade to bower@1.7.5.

Overview

uglify-js is a JavaScript parser, minifier, compressor and beautifier toolkit.

Tom MacWright discovered that UglifyJS versions 2.4.23 and earlier are affected by a vulnerability which allows a specially crafted Javascript file to have altered functionality after minification. This bug was demonstrated by Yan to allow potentially malicious code to be hidden within secure code, activated by minification.

Details

In Boolean algebra, DeMorgan's laws describe the relationships between conjunctions (&&), disjunctions (||) and negations (!). In Javascript form, they state that:

 !(a && b) === (!a) || (!b)
 !(a || b) === (!a) && (!b)

The law does not hold true when one of the values is not a boolean however.

Vulnerable versions of UglifyJS do not account for this restriction, and erroneously apply the laws to a statement if it can be reduced in length by it.

Consider this authentication function:

function isTokenValid(user) {
    var timeLeft =
        !!config && // config object exists
        !!user.token && // user object has a token
        !user.token.invalidated && // token is not explicitly invalidated
        !config.uninitialized && // config is initialized
        !config.ignoreTimestamps && // don't ignore timestamps
        getTimeLeft(user.token.expiry); // > 0 if expiration is in the future

    // The token must not be expired
    return timeLeft > 0;
}

function getTimeLeft(expiry) {
  return expiry - getSystemTime();
}

When minified with a vulnerable version of UglifyJS, it will produce the following insecure output, where a token will never expire:

( Formatted for readability )

function isTokenValid(user) {
    var timeLeft = !(                       // negation
        !config                             // config object does not exist
        || !user.token                      // user object does not have a token
        || user.token.invalidated           // token is explicitly invalidated
        || config.uninitialized             // config isn't initialized
        || config.ignoreTimestamps          // ignore timestamps
        || !getTimeLeft(user.token.expiry)  // > 0 if expiration is in the future
    );
    return timeLeft > 0
}

function getTimeLeft(expiry) {
    return expiry - getSystemTime()
}

Remediation

Upgrade UglifyJS to version 2.4.24 or higher.

References

medium severity

Time of Check Time of Use (TOCTOU)

  • Vulnerable module: chownr
  • Introduced through: npm@2.1.7

Detailed paths

  • Introduced through: steroids@4.0.10 npm@2.1.7 chownr@0.0.2
    Remediation: Upgrade to npm@6.6.0.
  • Introduced through: steroids@4.0.10 npm@2.1.7 npm-registry-client@4.0.5 chownr@0.0.2
    Remediation: Upgrade to npm@2.14.0.

Overview

chownr is a package that takes the same arguments as fs.chown()

Affected versions of this package are vulnerable to Time of Check Time of Use (TOCTOU). Affected versions of this package are vulnerable toTime of Check Time of Use (TOCTOU) attacks.

It does not dereference symbolic links and changes the owner of the link, which can trick it into descending into unintended trees if a non-symlink is replaced by a symlink at a critical moment:

      fs.lstat(pathChild, function(er, stats) {
        if (er)
          return cb(er)
        if (!stats.isSymbolicLink())
          chownr(pathChild, uid, gid, then)

Remediation

Upgrade chownr to version 1.1.0 or higher.

References

medium severity

Arbitrary File Write via Archive Extraction (Zip Slip)

  • Vulnerable module: decompress
  • Introduced through: yeoman-generator@0.17.7 and generator-steroids@1.0.18

Detailed paths

  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7
    Remediation: Upgrade to yeoman-generator@0.24.1.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7

Overview

decompress is a package that can be used for extracting archives.

Affected versions of this package are vulnerable to Arbitrary File Write via Archive Extraction (Zip Slip). It is possible to bypass the security measures provided by decompress and conduct ZIP path traversal through symlinks.

PoC

const decompress = require('decompress');

decompress('slip.tar.gz', 'dist').then(files => {
    console.log('done!');
});

Details

It is exploited using a specially crafted zip archive, that holds path traversal filenames. When exploited, a filename in a malicious archive is concatenated to the target extraction directory, which results in the final path ending up outside of the target folder. For instance, a zip may hold a file with a "../../file.exe" location and thus break out of the target folder. If an executable or a configuration file is overwritten with a file containing malicious code, the problem can turn into an arbitrary code execution issue quite easily.

The following is an example of a zip archive with one benign file and one malicious file. Extracting the malicous file will result in traversing out of the target folder, ending up in /root/.ssh/ overwriting the authorized_keys file:


+2018-04-15 22:04:29 ..... 19 19 good.txt

+2018-04-15 22:04:42 ..... 20 20 ../../../../../../root/.ssh/authorized_keys

Remediation

Upgrade decompress to version 4.2.1 or higher.

References

medium severity

Arbitrary File Write via Archive Extraction (Zip Slip)

  • Vulnerable module: decompress-tar
  • Introduced through: yeoman-generator@0.17.7 and generator-steroids@1.0.18

Detailed paths

  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-tar@1.0.3
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-tar@1.0.3

Overview

decompress-tar is a tar plugin for decompress.

Affected versions of this package are vulnerable to Arbitrary File Write via Archive Extraction (Zip Slip). It is possible to bypass the security measures provided by decompress and conduct ZIP path traversal through symlinks.

PoC

const decompress = require('decompress');

decompress('slip.tar.gz', 'dist').then(files => {
    console.log('done!');
});

Details

It is exploited using a specially crafted zip archive, that holds path traversal filenames. When exploited, a filename in a malicious archive is concatenated to the target extraction directory, which results in the final path ending up outside of the target folder. For instance, a zip may hold a file with a "../../file.exe" location and thus break out of the target folder. If an executable or a configuration file is overwritten with a file containing malicious code, the problem can turn into an arbitrary code execution issue quite easily.

The following is an example of a zip archive with one benign file and one malicious file. Extracting the malicous file will result in traversing out of the target folder, ending up in /root/.ssh/ overwriting the authorized_keys file:


+2018-04-15 22:04:29 ..... 19 19 good.txt

+2018-04-15 22:04:42 ..... 20 20 ../../../../../../root/.ssh/authorized_keys

Remediation

There is no fixed version for decompress-tar.

References

medium severity

Cross-site Scripting (XSS)

  • Vulnerable module: handlebars
  • Introduced through: bower@1.3.8

Detailed paths

  • Introduced through: steroids@4.0.10 bower@1.3.8 handlebars@1.3.0
    Remediation: Upgrade to bower@1.7.5.

Overview

handlebars provides the power necessary to let you build semantic templates.

When using attributes without quotes in a handlebars template, an attacker can manipulate the input to introduce additional attributes, potentially executing code. This may lead to a Cross-site Scripting (XSS) vulnerability, assuming an attacker can influence the value entered into the template. If the handlebars template is used to render user-generated content, this vulnerability may escalate to a persistent XSS vulnerability.

Details

Cross-Site Scripting (XSS) attacks occur when an attacker tricks a user’s browser to execute malicious JavaScript code in the context of a victim’s domain. Such scripts can steal the user’s session cookies for the domain, scrape or modify its content, and perform or modify actions on the user’s behalf, actions typically blocked by the browser’s Same Origin Policy.

These attacks are possible by escaping the context of the web application and injecting malicious scripts in an otherwise trusted website. These scripts can introduce additional attributes (say, a "new" option in a dropdown list or a new link to a malicious site) and can potentially execute code on the clients side, unbeknown to the victim. This occurs when characters like < > " ' are not escaped properly.

There are a few types of XSS:

  • Persistent XSS is an attack in which the malicious code persists into the web app’s database.
  • Reflected XSS is an which the website echoes back a portion of the request. The attacker needs to trick the user into clicking a malicious link (for instance through a phishing email or malicious JS on another page), which triggers the XSS attack.
  • DOM-based XSS is an that occurs purely in the browser when client-side JavaScript echoes back a portion of the URL onto the page. DOM-Based XSS is notoriously hard to detect, as the server never gets a chance to see the attack taking place.

Example:

Assume handlebars was used to display user comments and avatar, using the following template: <img src={{avatarUrl}}><pre>{{comment}}</pre>

If an attacker spoofed their avatar URL and provided the following value: http://evil.org/avatar.png onload=alert(document.cookie)

The resulting HTML would be the following, triggering the script once the image loads: <img src=http://evil.org/avatar.png onload=alert(document.cookie)><pre>Gotcha!</pre>

References

medium severity

Prototype Pollution

  • Vulnerable module: handlebars
  • Introduced through: bower@1.3.8

Detailed paths

  • Introduced through: steroids@4.0.10 bower@1.3.8 handlebars@1.3.0
    Remediation: Upgrade to bower@1.7.5.

Overview

handlebars is an extension to the Mustache templating language.

Affected versions of this package are vulnerable to Prototype Pollution when selecting certain compiling options to compile templates coming from an untrusted source.

POC

<script src="https://cdn.jsdelivr.net/npm/handlebars@latest/dist/handlebars.js"></script> 
<script> 
// compile the template 

var s2 = `{{'a/.") || alert("Vulnerable Handlebars JS when compiling in compat mode'}}`; 
var template = Handlebars.compile(s2, { 
compat: true 
}); 
// execute the compiled template and print the output to the console console.log(template({})); 
</script>

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 merge
  • Property 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

How to prevent

  1. Freeze the prototype— use Object.freeze (Object.prototype).
  2. Require schema validation of JSON input.
  3. Avoid using unsafe recursive merge functions.
  4. Consider using objects without prototypes (for example, Object.create(null)), breaking the prototype chain and preventing pollution.
  5. As a best practice use Map instead of Object.

For more information on this vulnerability type:

Arteau, Oliver. “JavaScript prototype pollution attack in NodeJS application.” GitHub, 26 May 2018

Remediation

Upgrade handlebars to version 4.7.7 or higher.

References

medium severity

Prototype Pollution

  • Vulnerable module: handlebars
  • Introduced through: bower@1.3.8

Detailed paths

  • Introduced through: steroids@4.0.10 bower@1.3.8 handlebars@1.3.0
    Remediation: Upgrade to bower@1.7.5.

Overview

handlebars is an extension to the Mustache templating language.

Affected versions of this package are vulnerable to Prototype Pollution. Prototype access to the template engine allows for potential code execution.

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:

  1. CCC
  2. CC+C
  3. C+CC
  4. 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 handlebars to version 4.6.0 or higher.

References

medium severity

Remote Code Execution (RCE)

  • Vulnerable module: handlebars
  • Introduced through: bower@1.3.8

Detailed paths

  • Introduced through: steroids@4.0.10 bower@1.3.8 handlebars@1.3.0
    Remediation: Upgrade to bower@1.7.5.

Overview

handlebars is an extension to the Mustache templating language.

Affected versions of this package are vulnerable to Remote Code Execution (RCE) when selecting certain compiling options to compile templates coming from an untrusted source.

POC

<script src="https://cdn.jsdelivr.net/npm/handlebars@latest/dist/handlebars.js"></script> 
<script> 
// compile the template 
var s = ` 
{{#with (__lookupGetter__ "__proto__")}} 
{{#with (./constructor.getOwnPropertyDescriptor . "valueOf")}} 
{{#with ../constructor.prototype}} 
{{../../constructor.defineProperty . "hasOwnProperty" ..}} 
{{/with}} 
{{/with}} 
{{/with}} 
{{#with "constructor"}} 
{{#with split}} 
{{pop (push "alert('Vulnerable Handlebars JS when compiling in strict mode');")}} 
{{#with .}} 
{{#with (concat (lookup join (slice 0 1)))}} 
{{#each (slice 2 3)}} 
{{#with (apply 0 ../..)}} 
{{.}} 
{{/with}} 
{{/each}} 
{{/with}} 
{{/with}} 
{{/with}} 
{{/with}} 
`;
var template = Handlebars.compile(s, { 
strict: true 
}); 
// execute the compiled template and print the output to the console console.log(template({})); 
</script>

Remediation

Upgrade handlebars to version 4.7.7 or higher.

References

medium severity

Prototype Pollution

  • Vulnerable module: hoek
  • Introduced through: request@2.27.0, npm@2.1.7 and others

Detailed paths

  • Introduced through: steroids@4.0.10 request@2.27.0 hawk@1.0.0 hoek@0.9.1
    Remediation: Upgrade to request@2.82.0.
  • Introduced through: steroids@4.0.10 request@2.27.0 hawk@1.0.0 boom@0.4.2 hoek@0.9.1
    Remediation: Upgrade to request@2.82.0.
  • Introduced through: steroids@4.0.10 request@2.27.0 hawk@1.0.0 sntp@0.2.4 hoek@0.9.1
    Remediation: Upgrade to request@2.82.0.
  • Introduced through: steroids@4.0.10 npm@2.1.7 request@2.47.0 hawk@1.1.1 hoek@0.9.1
    Remediation: Upgrade to npm@3.0.0.
  • Introduced through: steroids@4.0.10 bower@1.3.8 request@2.36.0 hawk@1.0.0 hoek@0.9.1
    Remediation: Upgrade to bower@1.7.5.
  • Introduced through: steroids@4.0.10 request@2.27.0 hawk@1.0.0 cryptiles@0.2.2 boom@0.4.2 hoek@0.9.1
    Remediation: Upgrade to request@2.82.0.
  • Introduced through: steroids@4.0.10 npm@2.1.7 request@2.47.0 hawk@1.1.1 boom@0.4.2 hoek@0.9.1
    Remediation: Upgrade to npm@3.0.0.
  • Introduced through: steroids@4.0.10 bower@1.3.8 request@2.36.0 hawk@1.0.0 boom@0.4.2 hoek@0.9.1
    Remediation: Upgrade to bower@1.7.5.
  • Introduced through: steroids@4.0.10 npm@2.1.7 request@2.47.0 hawk@1.1.1 sntp@0.2.4 hoek@0.9.1
    Remediation: Upgrade to npm@3.0.0.
  • Introduced through: steroids@4.0.10 bower@1.3.8 request@2.36.0 hawk@1.0.0 sntp@0.2.4 hoek@0.9.1
    Remediation: Upgrade to bower@1.7.5.
  • Introduced through: steroids@4.0.10 bower@1.3.8 bower-registry-client@0.2.4 request@2.51.0 hawk@1.1.1 hoek@0.9.1
    Remediation: Upgrade to bower@1.6.2.
  • Introduced through: steroids@4.0.10 bower@1.3.8 insight@0.3.1 request@2.27.0 hawk@1.0.0 hoek@0.9.1
    Remediation: Upgrade to bower@1.3.9.
  • Introduced through: steroids@4.0.10 npm@2.1.7 request@2.47.0 hawk@1.1.1 cryptiles@0.2.2 boom@0.4.2 hoek@0.9.1
    Remediation: Upgrade to npm@3.0.0.
  • Introduced through: steroids@4.0.10 bower@1.3.8 request@2.36.0 hawk@1.0.0 cryptiles@0.2.2 boom@0.4.2 hoek@0.9.1
    Remediation: Upgrade to bower@1.7.5.
  • Introduced through: steroids@4.0.10 bower@1.3.8 bower-registry-client@0.2.4 request@2.51.0 hawk@1.1.1 boom@0.4.2 hoek@0.9.1
    Remediation: Upgrade to bower@1.6.2.
  • Introduced through: steroids@4.0.10 bower@1.3.8 insight@0.3.1 request@2.27.0 hawk@1.0.0 boom@0.4.2 hoek@0.9.1
    Remediation: Upgrade to bower@1.3.9.
  • Introduced through: steroids@4.0.10 bower@1.3.8 bower-registry-client@0.2.4 request@2.51.0 hawk@1.1.1 sntp@0.2.4 hoek@0.9.1
    Remediation: Upgrade to bower@1.6.2.
  • Introduced through: steroids@4.0.10 bower@1.3.8 insight@0.3.1 request@2.27.0 hawk@1.0.0 sntp@0.2.4 hoek@0.9.1
    Remediation: Upgrade to bower@1.3.9.
  • Introduced through: steroids@4.0.10 bower@1.3.8 bower-registry-client@0.2.4 request@2.51.0 hawk@1.1.1 cryptiles@0.2.2 boom@0.4.2 hoek@0.9.1
    Remediation: Upgrade to bower@1.6.2.
  • Introduced through: steroids@4.0.10 bower@1.3.8 insight@0.3.1 request@2.27.0 hawk@1.0.0 cryptiles@0.2.2 boom@0.4.2 hoek@0.9.1
    Remediation: Upgrade to bower@1.3.9.
  • Introduced through: steroids@4.0.10 winston@0.7.3 request@2.16.6 hawk@0.10.2 hoek@0.7.6
    Remediation: Upgrade to winston@0.8.0.
  • Introduced through: steroids@4.0.10 winston@0.7.3 request@2.16.6 hawk@0.10.2 boom@0.3.8 hoek@0.7.6
    Remediation: Upgrade to winston@0.8.0.
  • Introduced through: steroids@4.0.10 winston@0.7.3 request@2.16.6 hawk@0.10.2 sntp@0.1.4 hoek@0.7.6
    Remediation: Upgrade to winston@0.8.0.
  • Introduced through: steroids@4.0.10 winston@0.7.3 request@2.16.6 hawk@0.10.2 cryptiles@0.1.3 boom@0.3.8 hoek@0.7.6
    Remediation: Upgrade to winston@0.8.0.

Overview

hoek is an Utility methods for the hapi ecosystem.

Affected versions of this package are vulnerable to Prototype Pollution. The utilities function allow modification of the Object prototype. If an attacker can control part of the structure passed to this function, they could add or modify an existing property.

PoC by Olivier Arteau (HoLyVieR)

var Hoek = require('hoek');
var malicious_payload = '{"__proto__":{"oops":"It works !"}}';

var a = {};
console.log("Before : " + a.oops);
Hoek.merge({}, JSON.parse(malicious_payload));
console.log("After : " + a.oops);

Details

Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.

The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.

Let’s take the following regular expression as an example:

regex = /A(B|C+)+D/

This regular expression accomplishes the following:

  • A The string must start with the letter 'A'
  • (B|C+)+ The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the + matches one or more times). The + at the end of this section states that we can look for one or more matches of this section.
  • D Finally, we ensure this section of the string ends with a 'D'

The expression would match inputs such as ABBD, ABCCCCD, ABCBCCCD and ACCCCCD

It most cases, it doesn't take very long for a regex engine to find a match:

$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total

$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total

The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.

Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.

Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:

  1. CCC
  2. CC+C
  3. C+CC
  4. C+C+C.

The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.

From there, the number of steps the engine must use to validate a string just continues to grow.

String Number of C's Number of steps
ACCCX 3 38
ACCCCX 4 71
ACCCCCX 5 136
ACCCCCCCCCCCCCCX 14 65,553

By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.

Remediation

Upgrade hoek to version 4.2.1, 5.0.3 or higher.

References

medium severity

Timing Attack

  • Vulnerable module: http-signature
  • Introduced through: request@2.27.0, bower@1.3.8 and others

Detailed paths

  • Introduced through: steroids@4.0.10 request@2.27.0 http-signature@0.10.1
    Remediation: Upgrade to request@2.66.0.
  • Introduced through: steroids@4.0.10 bower@1.3.8 request@2.36.0 http-signature@0.10.1
    Remediation: Upgrade to bower@1.7.5.
  • Introduced through: steroids@4.0.10 npm@2.1.7 request@2.47.0 http-signature@0.10.1
    Remediation: Upgrade to npm@2.14.15.
  • Introduced through: steroids@4.0.10 bower@1.3.8 bower-registry-client@0.2.4 request@2.51.0 http-signature@0.10.1
    Remediation: Upgrade to bower@1.6.2.
  • Introduced through: steroids@4.0.10 bower@1.3.8 insight@0.3.1 request@2.27.0 http-signature@0.10.1
    Remediation: Upgrade to bower@1.3.9.

Overview

http-signature is a reference implementation of Joyent's HTTP Signature scheme.

Affected versions of the package are vulnerable to Timing Attacks due to time-variable comparison of signatures.

The library implemented a character to character comparison, similar to the built-in string comparison mechanism, ===, and not a time constant string comparison. As a result, the comparison will fail faster when the first characters in the signature are incorrect. An attacker can use this difference to perform a timing attack, essentially allowing them to guess the signature one character at a time.

You can read more about timing attacks in Node.js on the Snyk blog.

Remediation

Upgrade http-signature to version 1.0.0 or higher.

References

medium severity

Denial of Service (DoS)

  • Vulnerable module: js-yaml
  • Introduced through: js-yaml@3.0.2 and bower@1.3.8

Detailed paths

  • Introduced through: steroids@4.0.10 js-yaml@3.0.2
    Remediation: Upgrade to js-yaml@3.13.0.
  • Introduced through: steroids@4.0.10 bower@1.3.8 insight@0.3.1 configstore@0.2.3 js-yaml@3.0.2
    Remediation: Upgrade to bower@1.3.9.

Overview

js-yaml is a human-friendly data serialization language.

Affected versions of this package are vulnerable to Denial of Service (DoS). The parsing of a specially crafted YAML file may exhaust the system resources.

Details

Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.

The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.

Let’s take the following regular expression as an example:

regex = /A(B|C+)+D/

This regular expression accomplishes the following:

  • A The string must start with the letter 'A'
  • (B|C+)+ The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the + matches one or more times). The + at the end of this section states that we can look for one or more matches of this section.
  • D Finally, we ensure this section of the string ends with a 'D'

The expression would match inputs such as ABBD, ABCCCCD, ABCBCCCD and ACCCCCD

It most cases, it doesn't take very long for a regex engine to find a match:

$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total

$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total

The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.

Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.

Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:

  1. CCC
  2. CC+C
  3. C+CC
  4. 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 js-yaml to version 3.13.0 or higher.

References

medium severity

Prototype Pollution

  • Vulnerable module: lodash
  • Introduced through: yeoman-generator@0.17.7, bower@1.3.8 and others

Detailed paths

  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.23.0.
  • Introduced through: steroids@4.0.10 bower@1.3.8 inquirer@0.5.1 lodash@2.4.2
    Remediation: Upgrade to bower@1.7.5.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 cheerio@0.17.0 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.19.0.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 file-utils@0.2.2 lodash@2.4.2
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 findup-sync@0.1.3 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.21.0.
  • Introduced through: steroids@4.0.10 grunt@0.4.5 findup-sync@0.1.3 lodash@2.4.2
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 gruntfile-editor@0.2.0 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.19.0.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 inquirer@0.7.3 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.21.0.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 lodash@2.4.2
  • Introduced through: steroids@4.0.10 grunt@0.4.5 grunt-legacy-log@0.1.3 lodash@2.4.2
    Remediation: Upgrade to grunt@1.0.0.
  • Introduced through: steroids@4.0.10 bower@1.3.8 insight@0.3.1 inquirer@0.4.1 lodash@2.4.2
    Remediation: Upgrade to bower@1.7.5.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 cheerio@0.17.0 lodash@2.4.2
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 file-utils@0.2.2 lodash@2.4.2
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 findup-sync@0.1.3 lodash@2.4.2
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 gruntfile-editor@0.2.0 ast-query@0.2.5 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.19.0.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 gruntfile-editor@0.2.0 lodash@2.4.2
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 inquirer@0.7.3 lodash@2.4.2
  • Introduced through: steroids@4.0.10 grunt@0.4.5 grunt-legacy-log@0.1.3 grunt-legacy-log-utils@0.1.1 lodash@2.4.2
    Remediation: Upgrade to grunt@1.0.3.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 gruntfile-editor@0.2.0 ast-query@0.2.5 lodash@2.4.2
  • Introduced through: steroids@4.0.10 grunt@0.4.5 lodash@0.9.2
    Remediation: Upgrade to grunt@1.0.0.
  • Introduced through: steroids@4.0.10 grunt@0.4.5 grunt-legacy-util@0.2.0 lodash@0.9.2
    Remediation: Upgrade to grunt@1.0.3.
  • Introduced through: steroids@4.0.10 inquirer@0.3.4 lodash@1.2.1
    Remediation: Upgrade to inquirer@0.12.0.
  • Introduced through: steroids@4.0.10 lodash@2.4.1
    Remediation: Upgrade to lodash@4.17.16.

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 merge
  • Property 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

How to prevent

  1. Freeze the prototype— use Object.freeze (Object.prototype).
  2. Require schema validation of JSON input.
  3. Avoid using unsafe recursive merge functions.
  4. Consider using objects without prototypes (for example, Object.create(null)), breaking the prototype chain and preventing pollution.
  5. As a best practice use Map instead of Object.

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 4.17.16 or higher.

References

medium severity

Prototype Pollution

  • Vulnerable module: lodash
  • Introduced through: yeoman-generator@0.17.7, bower@1.3.8 and others

Detailed paths

  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.23.0.
  • Introduced through: steroids@4.0.10 bower@1.3.8 inquirer@0.5.1 lodash@2.4.2
    Remediation: Upgrade to bower@1.7.5.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 cheerio@0.17.0 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.19.0.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 file-utils@0.2.2 lodash@2.4.2
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 findup-sync@0.1.3 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.21.0.
  • Introduced through: steroids@4.0.10 grunt@0.4.5 findup-sync@0.1.3 lodash@2.4.2
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 gruntfile-editor@0.2.0 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.19.0.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 inquirer@0.7.3 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.21.0.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 lodash@2.4.2
  • Introduced through: steroids@4.0.10 grunt@0.4.5 grunt-legacy-log@0.1.3 lodash@2.4.2
    Remediation: Upgrade to grunt@1.0.0.
  • Introduced through: steroids@4.0.10 bower@1.3.8 insight@0.3.1 inquirer@0.4.1 lodash@2.4.2
    Remediation: Upgrade to bower@1.7.5.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 cheerio@0.17.0 lodash@2.4.2
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 file-utils@0.2.2 lodash@2.4.2
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 findup-sync@0.1.3 lodash@2.4.2
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 gruntfile-editor@0.2.0 ast-query@0.2.5 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.19.0.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 gruntfile-editor@0.2.0 lodash@2.4.2
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 inquirer@0.7.3 lodash@2.4.2
  • Introduced through: steroids@4.0.10 grunt@0.4.5 grunt-legacy-log@0.1.3 grunt-legacy-log-utils@0.1.1 lodash@2.4.2
    Remediation: Upgrade to grunt@1.0.3.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 gruntfile-editor@0.2.0 ast-query@0.2.5 lodash@2.4.2
  • Introduced through: steroids@4.0.10 grunt@0.4.5 lodash@0.9.2
    Remediation: Upgrade to grunt@1.0.0.
  • Introduced through: steroids@4.0.10 grunt@0.4.5 grunt-legacy-util@0.2.0 lodash@0.9.2
    Remediation: Upgrade to grunt@1.0.3.
  • Introduced through: steroids@4.0.10 inquirer@0.3.4 lodash@1.2.1
    Remediation: Upgrade to inquirer@0.12.0.
  • Introduced through: steroids@4.0.10 lodash@2.4.1
    Remediation: Upgrade to lodash@4.17.5.

Overview

lodash is a modern JavaScript utility library delivering modularity, performance, & extras.

Affected versions of this package are vulnerable to Prototype Pollution. The utilities function allow modification of the Object prototype. If an attacker can control part of the structure passed to this function, they could add or modify an existing property.

PoC by Olivier Arteau (HoLyVieR)

var _= require('lodash');
var malicious_payload = '{"__proto__":{"oops":"It works !"}}';

var a = {};
console.log("Before : " + a.oops);
_.merge({}, JSON.parse(malicious_payload));
console.log("After : " + a.oops);

Details

Prototype Pollution is a vulnerability affecting JavaScript. Prototype Pollution refers to the ability to inject properties into existing JavaScript language construct prototypes, such as objects. JavaScript allows all Object attributes to be altered, including their magical attributes such as _proto_, constructor and prototype. An attacker manipulates these attributes to overwrite, or pollute, a JavaScript application object prototype of the base object by injecting other values. Properties on the Object.prototype are then inherited by all the JavaScript objects through the prototype chain. When that happens, this leads to either denial of service by triggering JavaScript exceptions, or it tampers with the application source code to force the code path that the attacker injects, thereby leading to remote code execution.

There are two main ways in which the pollution of prototypes occurs:

  • Unsafe Object recursive merge
  • Property 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

How to prevent

  1. Freeze the prototype— use Object.freeze (Object.prototype).
  2. Require schema validation of JSON input.
  3. Avoid using unsafe recursive merge functions.
  4. Consider using objects without prototypes (for example, Object.create(null)), breaking the prototype chain and preventing pollution.
  5. As a best practice use Map instead of Object.

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

Regular Expression Denial of Service (ReDoS)

  • Vulnerable module: lodash
  • Introduced through: yeoman-generator@0.17.7, bower@1.3.8 and others

Detailed paths

  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.23.0.
  • Introduced through: steroids@4.0.10 bower@1.3.8 inquirer@0.5.1 lodash@2.4.2
    Remediation: Upgrade to bower@1.7.5.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 cheerio@0.17.0 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.19.0.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 file-utils@0.2.2 lodash@2.4.2
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 findup-sync@0.1.3 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.21.0.
  • Introduced through: steroids@4.0.10 grunt@0.4.5 findup-sync@0.1.3 lodash@2.4.2
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 gruntfile-editor@0.2.0 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.19.0.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 inquirer@0.7.3 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.21.0.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 lodash@2.4.2
  • Introduced through: steroids@4.0.10 grunt@0.4.5 grunt-legacy-log@0.1.3 lodash@2.4.2
    Remediation: Upgrade to grunt@1.0.0.
  • Introduced through: steroids@4.0.10 bower@1.3.8 insight@0.3.1 inquirer@0.4.1 lodash@2.4.2
    Remediation: Upgrade to bower@1.7.5.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 cheerio@0.17.0 lodash@2.4.2
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 file-utils@0.2.2 lodash@2.4.2
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 findup-sync@0.1.3 lodash@2.4.2
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 gruntfile-editor@0.2.0 ast-query@0.2.5 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.19.0.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 gruntfile-editor@0.2.0 lodash@2.4.2
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 inquirer@0.7.3 lodash@2.4.2
  • Introduced through: steroids@4.0.10 grunt@0.4.5 grunt-legacy-log@0.1.3 grunt-legacy-log-utils@0.1.1 lodash@2.4.2
    Remediation: Upgrade to grunt@1.0.3.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 gruntfile-editor@0.2.0 ast-query@0.2.5 lodash@2.4.2
  • Introduced through: steroids@4.0.10 grunt@0.4.5 lodash@0.9.2
    Remediation: Upgrade to grunt@1.0.0.
  • Introduced through: steroids@4.0.10 grunt@0.4.5 grunt-legacy-util@0.2.0 lodash@0.9.2
    Remediation: Upgrade to grunt@1.0.3.
  • Introduced through: steroids@4.0.10 inquirer@0.3.4 lodash@1.2.1
    Remediation: Upgrade to inquirer@0.12.0.
  • Introduced through: steroids@4.0.10 lodash@2.4.1
    Remediation: Upgrade to lodash@4.17.21.

Overview

lodash is a modern JavaScript utility library delivering modularity, performance, & extras.

Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS) via the toNumber, trim and trimEnd functions.

POC

var lo = require('lodash');

function build_blank (n) {
var ret = "1"
for (var i = 0; i < n; i++) {
ret += " "
}

return ret + "1";
}

var s = build_blank(50000)
var time0 = Date.now();
lo.trim(s)
var time_cost0 = Date.now() - time0;
console.log("time_cost0: " + time_cost0)

var time1 = Date.now();
lo.toNumber(s)
var time_cost1 = Date.now() - time1;
console.log("time_cost1: " + time_cost1)

var time2 = Date.now();
lo.trimEnd(s)
var time_cost2 = Date.now() - time2;
console.log("time_cost2: " + time_cost2)

Details

Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.

The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.

Let’s take the following regular expression as an example:

regex = /A(B|C+)+D/

This regular expression accomplishes the following:

  • A The string must start with the letter 'A'
  • (B|C+)+ The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the + matches one or more times). The + at the end of this section states that we can look for one or more matches of this section.
  • D Finally, we ensure this section of the string ends with a 'D'

The expression would match inputs such as ABBD, ABCCCCD, ABCBCCCD and ACCCCCD

It most cases, it doesn't take very long for a regex engine to find a match:

$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total

$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total

The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.

Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.

Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:

  1. CCC
  2. CC+C
  3. C+CC
  4. 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

Regular Expression Denial of Service (ReDoS)

  • Vulnerable module: lodash
  • Introduced through: yeoman-generator@0.17.7, bower@1.3.8 and others

Detailed paths

  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.23.0.
  • Introduced through: steroids@4.0.10 bower@1.3.8 inquirer@0.5.1 lodash@2.4.2
    Remediation: Upgrade to bower@1.7.5.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 cheerio@0.17.0 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.19.0.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 file-utils@0.2.2 lodash@2.4.2
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 findup-sync@0.1.3 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.21.0.
  • Introduced through: steroids@4.0.10 grunt@0.4.5 findup-sync@0.1.3 lodash@2.4.2
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 gruntfile-editor@0.2.0 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.19.0.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 inquirer@0.7.3 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.21.0.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 lodash@2.4.2
  • Introduced through: steroids@4.0.10 grunt@0.4.5 grunt-legacy-log@0.1.3 lodash@2.4.2
    Remediation: Upgrade to grunt@1.0.0.
  • Introduced through: steroids@4.0.10 bower@1.3.8 insight@0.3.1 inquirer@0.4.1 lodash@2.4.2
    Remediation: Upgrade to bower@1.7.5.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 cheerio@0.17.0 lodash@2.4.2
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 file-utils@0.2.2 lodash@2.4.2
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 findup-sync@0.1.3 lodash@2.4.2
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 gruntfile-editor@0.2.0 ast-query@0.2.5 lodash@2.4.2
    Remediation: Upgrade to yeoman-generator@0.19.0.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 gruntfile-editor@0.2.0 lodash@2.4.2
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 inquirer@0.7.3 lodash@2.4.2
  • Introduced through: steroids@4.0.10 grunt@0.4.5 grunt-legacy-log@0.1.3 grunt-legacy-log-utils@0.1.1 lodash@2.4.2
    Remediation: Upgrade to grunt@1.0.3.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 gruntfile-editor@0.2.0 ast-query@0.2.5 lodash@2.4.2
  • Introduced through: steroids@4.0.10 grunt@0.4.5 lodash@0.9.2
    Remediation: Upgrade to grunt@1.0.0.
  • Introduced through: steroids@4.0.10 grunt@0.4.5 grunt-legacy-util@0.2.0 lodash@0.9.2
    Remediation: Upgrade to grunt@1.0.3.
  • Introduced through: steroids@4.0.10 inquirer@0.3.4 lodash@1.2.1
    Remediation: Upgrade to inquirer@0.12.0.
  • Introduced through: steroids@4.0.10 lodash@2.4.1
    Remediation: Upgrade to lodash@4.17.11.

Overview

lodash is a modern JavaScript utility library delivering modularity, performance, & extras.

Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS). It parses dates using regex strings, which may cause a slowdown of 2 seconds per 50k characters.

Details

Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.

The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.

Let’s take the following regular expression as an example:

regex = /A(B|C+)+D/

This regular expression accomplishes the following:

  • A The string must start with the letter 'A'
  • (B|C+)+ The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the + matches one or more times). The + at the end of this section states that we can look for one or more matches of this section.
  • D Finally, we ensure this section of the string ends with a 'D'

The expression would match inputs such as ABBD, ABCCCCD, ABCBCCCD and ACCCCCD

It most cases, it doesn't take very long for a regex engine to find a match:

$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total

$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total

The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.

Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.

Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:

  1. CCC
  2. CC+C
  3. C+CC
  4. 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

Prototype Pollution

  • Vulnerable module: minimist
  • Introduced through: optimist@0.6.0, bower@1.3.8 and others

Detailed paths

  • Introduced through: steroids@4.0.10 optimist@0.6.0 minimist@0.0.10
  • Introduced through: steroids@4.0.10 bower@1.3.8 bower-config@0.5.3 optimist@0.6.1 minimist@0.0.10
  • Introduced through: steroids@4.0.10 bower@1.3.8 bower-registry-client@0.2.4 bower-config@0.5.3 optimist@0.6.1 minimist@0.0.10
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yosay@0.3.0 taketalk@0.1.1 minimist@0.1.0

Overview

minimist is a parse argument options module.

Affected versions of this package are vulnerable to Prototype Pollution. The library could be tricked into adding or modifying properties of Object.prototype using a constructor or __proto__ payload.

PoC by Snyk

require('minimist')('--__proto__.injected0 value0'.split(' '));
console.log(({}).injected0 === 'value0'); // true

require('minimist')('--constructor.prototype.injected1 value1'.split(' '));
console.log(({}).injected1 === 'value1'); // true

Details

Prototype Pollution is a vulnerability affecting JavaScript. Prototype Pollution refers to the ability to inject properties into existing JavaScript language construct prototypes, such as objects. JavaScript allows all Object attributes to be altered, including their magical attributes such as _proto_, constructor and prototype. An attacker manipulates these attributes to overwrite, or pollute, a JavaScript application object prototype of the base object by injecting other values. Properties on the Object.prototype are then inherited by all the JavaScript objects through the prototype chain. When that happens, this leads to either denial of service by triggering JavaScript exceptions, or it tampers with the application source code to force the code path that the attacker injects, thereby leading to remote code execution.

There are two main ways in which the pollution of prototypes occurs:

  • Unsafe Object recursive merge
  • Property 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

How to prevent

  1. Freeze the prototype— use Object.freeze (Object.prototype).
  2. Require schema validation of JSON input.
  3. Avoid using unsafe recursive merge functions.
  4. Consider using objects without prototypes (for example, Object.create(null)), breaking the prototype chain and preventing pollution.
  5. As a best practice use Map instead of Object.

For more information on this vulnerability type:

Arteau, Oliver. “JavaScript prototype pollution attack in NodeJS application.” GitHub, 26 May 2018

Remediation

Upgrade minimist to version 0.2.1, 1.2.3 or higher.

References

medium severity

Regular Expression Denial of Service (ReDoS)

  • Vulnerable module: ms
  • Introduced through: express@4.8.8

Detailed paths

  • Introduced through: steroids@4.0.10 express@4.8.8 debug@1.0.4 ms@0.6.2
    Remediation: Upgrade to express@4.12.4.
  • Introduced through: steroids@4.0.10 express@4.8.8 send@0.8.5 ms@0.6.2
    Remediation: Upgrade to express@4.12.4.
  • Introduced through: steroids@4.0.10 express@4.8.8 finalhandler@0.1.0 debug@1.0.4 ms@0.6.2
    Remediation: Upgrade to express@4.12.4.
  • Introduced through: steroids@4.0.10 express@4.8.8 send@0.8.5 debug@1.0.4 ms@0.6.2
    Remediation: Upgrade to express@4.12.4.
  • Introduced through: steroids@4.0.10 express@4.8.8 serve-static@1.5.4 send@0.8.5 ms@0.6.2
    Remediation: Upgrade to express@4.12.0.
  • Introduced through: steroids@4.0.10 express@4.8.8 serve-static@1.5.4 send@0.8.5 debug@1.0.4 ms@0.6.2
    Remediation: Upgrade to express@4.12.0.

Overview

ms is a tiny milisecond conversion utility.

Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS) attack when converting a time period string (i.e. "2 days", "1h") into a milliseconds integer. A malicious user could pass extremely long strings to ms(), causing the server to take a long time to process, subsequently blocking the event loop for that extended period.

Details

Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.

The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.

Let’s take the following regular expression as an example:

regex = /A(B|C+)+D/

This regular expression accomplishes the following:

  • A The string must start with the letter 'A'
  • (B|C+)+ The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the + matches one or more times). The + at the end of this section states that we can look for one or more matches of this section.
  • D Finally, we ensure this section of the string ends with a 'D'

The expression would match inputs such as ABBD, ABCCCCD, ABCBCCCD and ACCCCCD

It most cases, it doesn't take very long for a regex engine to find a match:

$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total

$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total

The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.

Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.

Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:

  1. CCC
  2. CC+C
  3. C+CC
  4. C+C+C.

The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.

From there, the number of steps the engine must use to validate a string just continues to grow.

String Number of C's Number of steps
ACCCX 3 38
ACCCCX 4 71
ACCCCCX 5 136
ACCCCCCCCCCCCCCX 14 65,553

By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.

Remediation

Upgrade ms to version 0.7.1 or higher.

References

medium severity

Content Injection due to quoteless attributes

  • Vulnerable module: mustache
  • Introduced through: generator-steroids@1.0.18

Detailed paths

  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 mustache@0.8.2

Overview

When using attributes without quotes in a mustache template, an attacker can manipulate the input to introduce additional attributes, potentially executing code. This may lead to a Cross-site Scripting (XSS) vulnerability, assuming an attacker can influence the value entered into the template. If the mustache template is used to render user-generated content, this vulnerability may escalate to a persistent XSS vulnerability.

Example

For example, assume mustache was used to display user comments, using the following template: <a href={{email}}>{{name}}</a><pre>{{comment}}</pre>

If an attacker spoofed his email address and provided the following value: jane@evil.org onload=alert(document.cookie)

The resulting HTML would be: <a href=wizard@evil.org onload=alert(document.cookie)>Evil Wizard</a><pre>Busted!</pre>

References

medium severity

Access Restriction Bypass

  • Vulnerable module: npm
  • Introduced through: npm@2.1.7

Detailed paths

  • Introduced through: steroids@4.0.10 npm@2.1.7
    Remediation: Upgrade to npm@5.7.1.

Overview

npm is a package manager for JavaScript.

Affected versions of this package are vulnerable to Access Restriction Bypass. It might allow local users to bypass intended filesystem access restrictions due to ownerships of /etc and /usr directories are being changed unexpectedly, related to a "correctMkdir" issue.

Remediation

Upgrade npm to version 5.7.1 or higher.

References

medium severity

Insertion of Sensitive Information into Log File

  • Vulnerable module: npm
  • Introduced through: npm@2.1.7

Detailed paths

  • Introduced through: steroids@4.0.10 npm@2.1.7
    Remediation: Upgrade to npm@6.14.6.

Overview

npm is a package manager for JavaScript.

Affected versions of this package are vulnerable to Insertion of Sensitive Information into Log File. The CLI supports URLs like <protocol>://[<user>[:<password>]@]<hostname>[:<port>][:][/]<path>. The password value is not redacted and is printed to stdout and also to any generated log files.

Remediation

Upgrade npm to version 6.14.6 or higher.

References

medium severity

npm Token Leak

  • Vulnerable module: npm
  • Introduced through: npm@2.1.7

Detailed paths

  • Introduced through: steroids@4.0.10 npm@2.1.7
    Remediation: Upgrade to npm@2.15.1.

Overview

This vulnerability could cause the unintentional leakage of bearer tokens. A design flaw in npm's registry allows an attacker to set up an HTTP server that could collect authentication information, and then use this authentication information to impersonate the users whose tokens they collected. The attacker could do anything the compromised users could do, including publishing new versions of packages.

Details

The primary npm registry has, since late 2014, used HTTP bearer tokens to authenticate requests from the npm command-line interface. Due to a design flaw in the CLI, these bearer tokens were sent with every request made by logged-in users, regardless of the destination of the request. (The bearers only should have been included for requests made against a registry or registries used for the current install.)

This flaw allows an attacker to set up an HTTP server that could collect authentication information. They could then use this information to impersonate the users whose tokens they collected. This impersonation would allow them to do anything the compromised users could do, including publishing new versions of packages.

With the fixes npm have released, the CLI will only send bearer tokens with requests made against a registry. npm’s CLI team believe that the fix won’t break any existing registry setups. However, it’s possible the change will be breaking in some cases, due to the large number of registry software suites used.

Remediation

  1. Upgrade npm to ">= 3.8.3 || >= 2.15.1"
  2. Invalidate your current npm bearer tokens

References

medium severity

Denial of Service (DoS)

  • Vulnerable module: qs
  • Introduced through: request@2.27.0, restler@3.2.2 and others

Detailed paths

  • Introduced through: steroids@4.0.10 request@2.27.0 qs@0.6.6
    Remediation: Upgrade to steroids@4.0.12.
  • Introduced through: steroids@4.0.10 restler@3.2.2 qs@0.6.6
    Remediation: Upgrade to restler@3.3.0.
  • Introduced through: steroids@4.0.10 bower@1.3.8 request@2.36.0 qs@0.6.6
    Remediation: Upgrade to bower@1.3.10.
  • Introduced through: steroids@4.0.10 bower@1.3.8 insight@0.3.1 request@2.27.0 qs@0.6.6
    Remediation: Upgrade to bower@1.3.9.
  • Introduced through: steroids@4.0.10 winston@0.7.3 request@2.16.6 qs@0.5.6
    Remediation: Upgrade to winston@0.8.0.

Overview

qs is a querystring parser that supports nesting and arrays, with a depth limit.

Affected versions of this package are vulnerable to Denial of Service (DoS). When parsing a string representing a deeply nested object, qs will block the event loop for long periods of time. Such a delay may hold up the server's resources, keeping it from processing other requests in the meantime, thus enabling a Denial-of-Service attack.

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:

  1. CCC
  2. CC+C
  3. C+CC
  4. 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 qs to version 1.0.0 or higher.

References

medium severity

Remote Memory Exposure

  • Vulnerable module: request
  • Introduced through: bower@1.3.8, request@2.27.0 and others

Detailed paths

  • Introduced through: steroids@4.0.10 bower@1.3.8 bower-registry-client@0.2.4 request@2.51.0
    Remediation: Upgrade to bower@1.6.2.
  • Introduced through: steroids@4.0.10 request@2.27.0
    Remediation: Upgrade to request@2.68.0.
  • Introduced through: steroids@4.0.10 bower@1.3.8 insight@0.3.1 request@2.27.0
    Remediation: Upgrade to bower@1.3.9.
  • Introduced through: steroids@4.0.10 bower@1.3.8 request@2.36.0
    Remediation: Upgrade to bower@1.7.5.
  • Introduced through: steroids@4.0.10 npm@2.1.7 request@2.47.0
    Remediation: Upgrade to npm@2.14.18.
  • Introduced through: steroids@4.0.10 prompt@0.2.11 winston@0.6.2 request@2.9.203
    Remediation: Upgrade to steroids@4.1.17.
  • Introduced through: steroids@4.0.10 winston@0.7.3 request@2.16.6
    Remediation: Upgrade to winston@0.8.0.

Overview

request is a simplified http request client.

Affected versions of this package are vulnerable to Remote Memory Exposure. A potential remote memory exposure vulnerability exists in request. If a request uses a multipart attachment and the body type option is number with value X, then X bytes of uninitialized memory will be sent in the body of the request.

Note that while the impact of this vulnerability is high (memory exposure), exploiting it is likely difficult, as the attacker needs to somehow control the body type of the request. One potential exploit scenario is when a request is composed based on JSON input, including the body type, allowing a malicious JSON to trigger the memory leak.

Details

Constructing a Buffer class with integer N creates a Buffer of length N with non zero-ed out memory. Example:

var x = new Buffer(100); // uninitialized Buffer of length 100
// vs
var x = new Buffer('100'); // initialized Buffer with value of '100'

Initializing a multipart body in such manner will cause uninitialized memory to be sent in the body of the request.

Proof of concept

var http = require('http')
var request = require('request')

http.createServer(function (req, res) {
  var data = ''
  req.setEncoding('utf8')
  req.on('data', function (chunk) {
    console.log('data')
    data += chunk
  })
  req.on('end', function () {
    // this will print uninitialized memory from the client
    console.log('Client sent:\n', data)
  })
  res.end()
}).listen(8000)

request({
  method: 'POST',
  uri: 'http://localhost:8000',
  multipart: [{ body: 1000 }]
},
function (err, res, body) {
  if (err) return console.error('upload failed:', err)
  console.log('sent')
})

Remediation

Upgrade request to version 2.68.0 or higher.

References

medium severity

Regular Expression Denial of Service (ReDoS)

  • Vulnerable module: semver
  • Introduced through: bower@1.3.8, npm@2.1.7 and others

Detailed paths

  • Introduced through: steroids@4.0.10 bower@1.3.8 semver@2.3.2
    Remediation: Upgrade to bower@1.5.0.
  • Introduced through: steroids@4.0.10 npm@2.1.7 semver@4.1.1
    Remediation: Upgrade to npm@2.6.0.
  • Introduced through: steroids@4.0.10 semver@2.3.1
    Remediation: Upgrade to semver@4.3.2.

Overview

semver is a semantic version parser used by npm.

Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS).

Overview

npm is a package manager for javascript.

Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS). The semver module uses regular expressions when parsing a version string. For a carefully crafted input, the time it takes to process these regular expressions is not linear to the length of the input. Since the semver module did not enforce a limit on the version string length, an attacker could provide a long string that would take up a large amount of resources, potentially taking a server down. This issue therefore enables a potential Denial of Service attack. This is a slightly differnt variant of a typical Regular Expression Denial of Service (ReDoS) vulnerability.

Details

<>

Remediation

Update to a version 4.3.2 or greater. From the issue description [2]: "Package version can no longer be more than 256 characters long. This prevents a situation in which parsing the version number can use exponentially more time and memory to parse, leading to a potential denial of service."

References

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:

  1. CCC
  2. CC+C
  3. C+CC
  4. C+C+C.

The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.

From there, the number of steps the engine must use to validate a string just continues to grow.

String Number of C's Number of steps
ACCCX 3 38
ACCCCX 4 71
ACCCCCX 5 136
ACCCCCCCCCCCCCCX 14 65,553

By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.

Remediation

Upgrade semver to version 4.3.2 or higher.

References

medium severity

Root Path Disclosure

  • Vulnerable module: send
  • Introduced through: express@4.8.8

Detailed paths

  • Introduced through: steroids@4.0.10 express@4.8.8 send@0.8.5
    Remediation: Upgrade to express@4.11.1.
  • Introduced through: steroids@4.0.10 express@4.8.8 serve-static@1.5.4 send@0.8.5
    Remediation: Upgrade to express@4.11.0.

Overview

Send is a library for streaming files from the file system as an http response. It supports partial responses (Ranges), conditional-GET negotiation, high test coverage, and granular events which may be leveraged to take appropriate actions in your application or framework.

Affected versions of this package are vulnerable to a Root Path Disclosure.

Remediation

Upgrade send to version 0.11.1 or higher. If a direct dependency update is not possible, use snyk wizard to patch this vulnerability.

References

medium severity

Uninitialized Memory Exposure

  • Vulnerable module: tunnel-agent
  • Introduced through: bower@1.3.8, npm@2.1.7 and others

Detailed paths

  • Introduced through: steroids@4.0.10 bower@1.3.8 request@2.36.0 tunnel-agent@0.4.3
    Remediation: Upgrade to bower@1.7.5.
  • Introduced through: steroids@4.0.10 npm@2.1.7 request@2.47.0 tunnel-agent@0.4.3
    Remediation: Upgrade to npm@3.0.0.
  • Introduced through: steroids@4.0.10 bower@1.3.8 bower-registry-client@0.2.4 request@2.51.0 tunnel-agent@0.4.3
    Remediation: Upgrade to bower@1.6.2.
  • Introduced through: steroids@4.0.10 request@2.27.0 tunnel-agent@0.3.0
    Remediation: Upgrade to request@2.81.0.
  • Introduced through: steroids@4.0.10 bower@1.3.8 insight@0.3.1 request@2.27.0 tunnel-agent@0.3.0
    Remediation: Upgrade to bower@1.3.9.
  • Introduced through: steroids@4.0.10 winston@0.7.3 request@2.16.6 tunnel-agent@0.2.0
    Remediation: Upgrade to winston@0.8.0.

Overview

tunnel-agent is HTTP proxy tunneling agent. Affected versions of the package are vulnerable to Uninitialized Memory Exposure.

A possible memory disclosure vulnerability exists when a value of type number is used to set the proxy.auth option of a request request and results in a possible uninitialized memory exposures in the request body.

This is a result of unobstructed use of the Buffer constructor, whose insecure default constructor increases the odds of memory leakage.

Details

Constructing a Buffer class with integer N creates a Buffer of length N with raw (not "zero-ed") memory.

In the following example, the first call would allocate 100 bytes of memory, while the second example will allocate the memory needed for the string "100":

// uninitialized Buffer of length 100
x = new Buffer(100);
// initialized Buffer with value of '100'
x = new Buffer('100');

tunnel-agent's request construction uses the default Buffer constructor as-is, making it easy to append uninitialized memory to an existing list. If the value of the buffer list is exposed to users, it may expose raw server side memory, potentially holding secrets, private data and code. This is a similar vulnerability to the infamous Heartbleed flaw in OpenSSL.

Proof of concept by ChALkeR

require('request')({
  method: 'GET',
  uri: 'http://www.example.com',
  tunnel: true,
  proxy:{
      protocol: 'http:',
      host:"127.0.0.1",
      port:8080,
      auth:80
  }
});

You can read more about the insecure Buffer behavior on our blog.

Similar vulnerabilities were discovered in request, mongoose, ws and sequelize.

Remediation

Upgrade tunnel-agent to version 0.6.0 or higher. Note This is vulnerable only for Node <=4

References

medium severity

Regular Expression Denial of Service (ReDoS)

  • Vulnerable module: uglify-js
  • Introduced through: bower@1.3.8

Detailed paths

  • Introduced through: steroids@4.0.10 bower@1.3.8 handlebars@1.3.0 uglify-js@2.3.6
    Remediation: Upgrade to bower@1.7.5.

Overview

The parse() function in the uglify-js package prior to version 2.6.0 is vulnerable to regular expression denial of service (ReDoS) attacks when long inputs of certain patterns are processed.

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:

  1. CCC
  2. CC+C
  3. C+CC
  4. 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 to version 2.6.0 or greater. If a direct dependency update is not possible, use snyk wizard to patch this vulnerability.

References

medium severity

Arbitrary Code Injection

  • Vulnerable module: underscore
  • Introduced through: js-yaml@3.0.2, grunt@0.4.5 and others

Detailed paths

  • Introduced through: steroids@4.0.10 js-yaml@3.0.2 argparse@0.1.16 underscore@1.7.0
    Remediation: Upgrade to js-yaml@3.2.7.
  • Introduced through: steroids@4.0.10 grunt@0.4.5 js-yaml@2.0.5 argparse@0.1.16 underscore@1.7.0
  • Introduced through: steroids@4.0.10 bower@1.3.8 insight@0.3.1 configstore@0.2.3 js-yaml@3.0.2 argparse@0.1.16 underscore@1.7.0
    Remediation: Upgrade to bower@1.3.9.

Overview

underscore is a JavaScript's functional programming helper library.

Affected versions of this package are vulnerable to Arbitrary Code Injection via the template function, particularly when the variable option is taken from _.templateSettings as it is not sanitized.

PoC

const _ = require('underscore');
_.templateSettings.variable = "a = this.process.mainModule.require('child_process').execSync('touch HELLO')";
const t = _.template("")();

Remediation

Upgrade underscore to version 1.13.0-2, 1.12.1 or higher.

References

low severity

Regular Expression Denial of Service (ReDoS)

  • Vulnerable module: debug
  • Introduced through: express@4.8.8, yeoman-generator@0.17.7 and others

Detailed paths

  • Introduced through: steroids@4.0.10 express@4.8.8 debug@1.0.4
    Remediation: Upgrade to express@4.15.5.
  • Introduced through: steroids@4.0.10 express@4.8.8 finalhandler@0.1.0 debug@1.0.4
    Remediation: Upgrade to express@4.15.0.
  • Introduced through: steroids@4.0.10 express@4.8.8 send@0.8.5 debug@1.0.4
    Remediation: Upgrade to express@4.15.5.
  • Introduced through: steroids@4.0.10 express@4.8.8 serve-static@1.5.4 send@0.8.5 debug@1.0.4
    Remediation: Upgrade to express@4.15.5.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 debug@1.0.5
    Remediation: Upgrade to yeoman-generator@0.18.0.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 debug@1.0.5

Overview

debug is a JavaScript debugging utility modelled after Node.js core's debugging technique..

debug uses printf-style formatting. Affected versions of this package are vulnerable to Regular expression Denial of Service (ReDoS) attacks via the the %o formatter (Pretty-print an Object all on a single line). It used a regular expression (/\s*\n\s*/g) in order to strip whitespaces and replace newlines with spaces, in order to join the data into a single line. This can cause a very low impact of about 2 seconds matching time for data 50k characters long.

Details

Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.

The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.

Let’s take the following regular expression as an example:

regex = /A(B|C+)+D/

This regular expression accomplishes the following:

  • A The string must start with the letter 'A'
  • (B|C+)+ The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the + matches one or more times). The + at the end of this section states that we can look for one or more matches of this section.
  • D Finally, we ensure this section of the string ends with a 'D'

The expression would match inputs such as ABBD, ABCCCCD, ABCBCCCD and ACCCCCD

It most cases, it doesn't take very long for a regex engine to find a match:

$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total

$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total

The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.

Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.

Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:

  1. CCC
  2. CC+C
  3. C+CC
  4. C+C+C.

The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.

From there, the number of steps the engine must use to validate a string just continues to grow.

String Number of C's Number of steps
ACCCX 3 38
ACCCCX 4 71
ACCCCCX 5 136
ACCCCCCCCCCCCCCX 14 65,553

By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.

Remediation

Upgrade debug to version 2.6.9, 3.1.0 or higher.

References

low severity

Regular Expression Denial of Service (ReDoS)

  • Vulnerable module: hawk
  • Introduced through: npm@2.1.7, bower@1.3.8 and others

Detailed paths

  • Introduced through: steroids@4.0.10 npm@2.1.7 request@2.47.0 hawk@1.1.1
    Remediation: Upgrade to npm@2.13.3.
  • Introduced through: steroids@4.0.10 bower@1.3.8 bower-registry-client@0.2.4 request@2.51.0 hawk@1.1.1
    Remediation: Upgrade to bower@1.6.2.
  • Introduced through: steroids@4.0.10 request@2.27.0 hawk@1.0.0
    Remediation: Upgrade to request@2.59.0.
  • Introduced through: steroids@4.0.10 bower@1.3.8 request@2.36.0 hawk@1.0.0
    Remediation: Upgrade to bower@1.7.5.
  • Introduced through: steroids@4.0.10 bower@1.3.8 insight@0.3.1 request@2.27.0 hawk@1.0.0
    Remediation: Upgrade to bower@1.3.9.
  • Introduced through: steroids@4.0.10 winston@0.7.3 request@2.16.6 hawk@0.10.2
    Remediation: Upgrade to winston@0.8.0.

Overview

hawk is an HTTP authentication scheme using a message authentication code (MAC) algorithm to provide partial HTTP request cryptographic verification.

Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS) attacks.

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:

  1. CCC
  2. CC+C
  3. C+CC
  4. 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.

You can read more about Regular Expression Denial of Service (ReDoS) on our blog.

References

low severity

Regular Expression Denial of Service (ReDoS)

  • Vulnerable module: mime
  • Introduced through: request@2.27.0, bower@1.3.8 and others

Detailed paths

  • Introduced through: steroids@4.0.10 request@2.27.0 mime@1.2.11
    Remediation: Upgrade to request@2.37.0.
  • Introduced through: steroids@4.0.10 request@2.27.0 form-data@0.1.4 mime@1.2.11
    Remediation: Upgrade to steroids@4.0.12.
  • Introduced through: steroids@4.0.10 bower@1.3.8 request@2.36.0 mime@1.2.11
    Remediation: Upgrade to bower@1.7.5.
  • Introduced through: steroids@4.0.10 express@4.8.8 send@0.8.5 mime@1.2.11
    Remediation: Upgrade to express@4.16.0.
  • Introduced through: steroids@4.0.10 winston@0.7.3 request@2.16.6 mime@1.2.11
    Remediation: Upgrade to winston@0.8.0.
  • Introduced through: steroids@4.0.10 bower@1.3.8 request@2.36.0 form-data@0.1.4 mime@1.2.11
    Remediation: Upgrade to bower@1.4.0.
  • Introduced through: steroids@4.0.10 npm@2.1.7 request@2.47.0 form-data@0.1.4 mime@1.2.11
    Remediation: Upgrade to npm@2.1.13.
  • Introduced through: steroids@4.0.10 bower@1.3.8 insight@0.3.1 request@2.27.0 mime@1.2.11
    Remediation: Open PR to patch mime@1.2.11.
  • Introduced through: steroids@4.0.10 express@4.8.8 serve-static@1.5.4 send@0.8.5 mime@1.2.11
    Remediation: Upgrade to express@4.16.0.
  • Introduced through: steroids@4.0.10 winston@0.7.3 request@2.16.6 form-data@0.0.10 mime@1.2.11
    Remediation: Upgrade to winston@0.8.0.
  • Introduced through: steroids@4.0.10 bower@1.3.8 insight@0.3.1 request@2.27.0 form-data@0.1.4 mime@1.2.11
    Remediation: Upgrade to bower@1.3.9.

Overview

mime is a comprehensive, compact MIME type module.

Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS). It uses regex the following regex /.*[\.\/\\]/ in its lookup, which can cause a slowdown of 2 seconds for 50k characters.

Details

Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.

The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.

Let’s take the following regular expression as an example:

regex = /A(B|C+)+D/

This regular expression accomplishes the following:

  • A The string must start with the letter 'A'
  • (B|C+)+ The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the + matches one or more times). The + at the end of this section states that we can look for one or more matches of this section.
  • D Finally, we ensure this section of the string ends with a 'D'

The expression would match inputs such as ABBD, ABCCCCD, ABCBCCCD and ACCCCCD

It most cases, it doesn't take very long for a regex engine to find a match:

$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total

$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total

The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.

Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.

Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:

  1. CCC
  2. CC+C
  3. C+CC
  4. C+C+C.

The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.

From there, the number of steps the engine must use to validate a string just continues to grow.

String Number of C's Number of steps
ACCCX 3 38
ACCCCX 4 71
ACCCCCX 5 136
ACCCCCCCCCCCCCCX 14 65,553

By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.

Remediation

Upgrade mime to version 1.4.1, 2.0.3 or higher.

References

low severity

Unauthorized File Access

  • Vulnerable module: npm
  • Introduced through: npm@2.1.7

Detailed paths

  • Introduced through: steroids@4.0.10 npm@2.1.7
    Remediation: Upgrade to npm@6.13.3.

Overview

npm is a package manager for JavaScript.

Affected versions of this package are vulnerable to Unauthorized File Access. It is possible for packages to create symlinks to files outside of thenode_modules folder through the bin field upon installation.

For npm, a properly constructed entry in the package.json bin field would allow a package publisher to create a symlink pointing to arbitrary files on a user’s system when the package is installed. This behaviour is possible through install scripts. This vulnerability bypasses a user using the --ignore-scripts install option.

Remediation

Upgrade npm to version 6.13.3 or higher.

References

low severity

Open Redirect

  • Vulnerable module: serve-static
  • Introduced through: express@4.8.8

Detailed paths

  • Introduced through: steroids@4.0.10 express@4.8.8 serve-static@1.5.4
    Remediation: Upgrade to express@4.9.0.

Overview

When using serve-static middleware version < 1.7.2 and it's configured to mount at the root, it creates an open redirect on the site.

Source: Node Security Project

Details

For example:

If a user visits http://example.com//www.google.com/%2e%2e they will be redirected to //www.google.com/%2e%2e, which some browsers interpret as http://www.google.com/%2e%2e.

Remediation

  • Update to version 1.7.2 or greater (or 1.6.5 if sticking to the 1.6.x line).
  • Disable redirects if not using the feature with 'redirect: false' option and cannot upgrade.

References

low severity

Regular Expression Denial of Service (ReDoS)

  • Vulnerable module: tar
  • Introduced through: bower@1.3.8, npm@2.1.7 and others

Detailed paths

  • Introduced through: steroids@4.0.10 bower@1.3.8 tar@0.1.20
    Remediation: Upgrade to bower@1.3.10.
  • Introduced through: steroids@4.0.10 npm@2.1.7 tar@1.0.3
    Remediation: Upgrade to npm@5.6.0.
  • Introduced through: steroids@4.0.10 npm@2.1.7 node-gyp@1.0.3 tar@1.0.3
    Remediation: Upgrade to npm@5.6.0.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-tar@1.0.3 tar@1.0.3
    Remediation: Upgrade to yeoman-generator@0.24.1.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-tarbz2@1.0.2 tar@1.0.3
    Remediation: Upgrade to yeoman-generator@0.24.1.
  • Introduced through: steroids@4.0.10 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-targz@1.0.3 tar@1.0.3
    Remediation: Upgrade to yeoman-generator@0.24.1.
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-tar@1.0.3 tar@1.0.3
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-tarbz2@1.0.2 tar@1.0.3
  • Introduced through: steroids@4.0.10 generator-steroids@1.0.18 yeoman-generator@0.17.7 download@1.0.7 decompress@1.0.7 decompress-targz@1.0.3 tar@1.0.3

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:

  1. CCC
  2. CC+C
  3. C+CC
  4. 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.

References

low severity

Uninitialized Memory Exposure

  • Vulnerable module: utile
  • Introduced through: prompt@0.2.11

Detailed paths

  • Introduced through: steroids@4.0.10 prompt@0.2.11 utile@0.2.1

Overview

utile is a drop-in replacement for util with some additional advantageous functions.

Affected versions of this package are vulnerable to Uninitialized Memory Exposure. A malicious user could extract sensitive data from uninitialized memory or to cause a DoS by passing in a large number, in setups where typed user input can be passed.

Note Uninitialized Memory Exposure impacts only Node.js 6.x or lower, Denial of Service impacts any Node.js version.

Details

The Buffer class on Node.js is a mutable array of binary data, and can be initialized with a string, array or number.

const buf1 = new Buffer([1,2,3]);
// creates a buffer containing [01, 02, 03]
const buf2 = new Buffer('test');
// creates a buffer containing ASCII bytes [74, 65, 73, 74]
const buf3 = new Buffer(10);
// creates a buffer of length 10

The first two variants simply create a binary representation of the value it received. The last one, however, pre-allocates a buffer of the specified size, making it a useful buffer, especially when reading data from a stream. When using the number constructor of Buffer, it will allocate the memory, but will not fill it with zeros. Instead, the allocated buffer will hold whatever was in memory at the time. If the buffer is not zeroed by using buf.fill(0), it may leak sensitive information like keys, source code, and system info.

Remediation

There is no fix version for utile.

References