Vulnerabilities in pkg:npm/highlight.js

PACKAGE
Advisory Identifier: GHSA-vfrc-7r7c-w9mx
Advisory Summary

CVE-2020-26237 is a MODERATE (CVSS 5.8) prototype pollution vulnerability (CWE-471: Modification of Assumed-Immutable Data (MAID)) affecting Highlight.js libraries in the npm ecosystem. The issue involves prototype pollution in highlight.js. Remediation is available by upgrading affected packages to version 9.18.2, 10.1.2.

2 Known Advisory Record(s)
Package Vulnerability Intelligence

pkg:npm/highlight.js

2 Known Advisory Record(s)

Vulnerability advisories affecting package pkg:npm/highlight.js. Select an advisory below to view technical details or fixes.

Advisory ID CVE / NVD Severity Summary
GHSA-vfrc-7r7c-w9mx CVE-2020-26237 MODERATE Prototype Pollution in highlight.js
GHSA-7wwv-vh3v-89cq - MODERATE ReDOS vulnerabities: multiple grammars

CVE-2020-26237 at a Glance

CVE Identifier CVE-2020-26237
GHSA Identifier GHSA-vfrc-7r7c-w9mx
Severity MODERATE
CVSS v3.1 Base Score 5.8
CWE Classification CWE-471: Modification of Assumed-Immutable Data (MAID)
Affected Product Highlight.js
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 5.8

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:N/I:H/A:N).

Attack Vector Network (AV:N)
Attack Complexity High (AC:H)
Privileges Required Low (PR:L)
User Interaction Required (UI:R)
Scope Changed (S:C)
Confidentiality None (C:N)
Integrity High (I:H)
Availability None (A:N)

How to Fix CVE-2020-26237

To remediate this vulnerability, upgrade all affected Highlight.js dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

highlight.js fixed: 9.18.2
npm install highlight.js@9.18.2
highlight.js fixed: 10.1.2
npm install highlight.js@10.1.2
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release:

npm ls highlight.js

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2020-26237, inspect your project dependencies using npm:

npm ls highlight.js

Analyze the terminal output to locate any version of Highlight.js in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 9.18.2), your application is affected.

Note: The npm ls highlight.js command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-471: Modification of Assumed-Immutable Data (MAID), where the product does not properly protect an assumed-immutable element from being modified by an attacker. In Highlight.js, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Impact Affected versions of this package are vulnerable to Prototype Pollution. A malicious HTML code block can be crafted that will result in prototype pollution of the base object's prototype during highlighting. If you allow users to insert custom HTML code blocks into your page/app via parsing Markdown code blocks (or similar) and do not filter the language names the user can provide you may be vulnerable. The pollution should just be harmless data but this can cause problems for applications not expecting these properties to exist and can result in strange behavior or application crashes, i.e. a potential DOS vector. _If your website or application does not render user provided data it should be unaffected._ ### Patches Versions 9.18.2 and 10.1.2 and newer include fixes for this vulnerability. If you are using version 7 or 8 you are encouraged to upgrade to a newer release. ### Workarounds #### Patch your library Manually patch your library to create null objects for both `languages` and `aliases`: ```js const HLJS = function(hljs) { // ... var languages = Object.create(null); var aliases = Object.create(null); ``` #### Filter out bad data from end users: Filter the language names that users are allowed to inject into your HTML to guarantee they are valid. ### References * [What is Prototype Pollution?](https://codeburst.io/what-is-prototype-pollution-49482fc4b638) * https://github.com/highlightjs/highlight.js/pull/2636 ### For more information If you have any questions or comments about this advisory: * Please file an issue against [highlight.js](https://github.com/highlightjs/highlight.js/issues/)

CVE-2020-26237 Affected Highlight.js Versions

2 component(s)
Fixed Versions:
9.18.210.1.2
Product / Package Ecosystem Affected Versions Fixed Version
highlight.js
npm
< 9.18.2
9.18.2
highlight.js
npm
≥ 10.0.0
< 10.1.2
10.1.2

References

Frequently Asked Questions

What is CVE-2020-26237?
CVE-2020-26237 is a security vulnerability in Highlight.js involving Prototype Pollution in highlight.js under CWE-471: Modification of Assumed-Immutable Data (MAID).
Which Highlight.js versions are affected?
Affected versions include releases prior to 9.18.2, 10.1.2 across affected packages: highlight.js.
What version fixes CVE-2020-26237?
Upgrading to 9.18.2, 10.1.2 (or the latest patched release for your respective branch) resolves the vulnerability.
Is highlight.js affected?
Yes, highlight.js is affected in releases prior to 9.18.2, 10.1.2. Upgrade your dependency to 9.18.2, 10.1.2 or later.
What is the CVSS score of CVE-2020-26237?
CVE-2020-26237 has a CVSS v3.1 base score of 5.8 (MODERATE) with vector string CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:N/I:H/A:N.
What CWE is associated with CVE-2020-26237?
CVE-2020-26237 is classified under CWE-471: Modification of Assumed-Immutable Data (MAID) (The product does not properly protect an assumed-immutable element from being modified by an attacker.).
How can I check npm dependencies for CVE-2020-26237?
Run the dependency tree command: 'npm ls highlight.js'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-vfrc-7r7c-w9mx",
  "modified" : "2022-10-20T13:52:50Z",
  "published" : "2020-11-24T22:58:41Z",
  "aliases" : [ "CVE-2020-26237" ],
  "summary" : "Prototype Pollution in highlight.js",
  "details" : "### Impact\n\nAffected versions of this package are vulnerable to Prototype Pollution.  A malicious HTML code block can be crafted that will result in prototype pollution of the base object's prototype during highlighting.  If you allow users to insert custom HTML code blocks into your page/app via parsing Markdown code blocks (or similar) and do not filter the language names the user can provide you may be vulnerable. \n\nThe pollution should just be harmless data but this can cause problems for applications not expecting these properties to exist and can result in strange behavior or application crashes, i.e. a potential DOS vector. \n\n_If your website or application does not render user provided data it should be unaffected._\n\n### Patches\n\nVersions 9.18.2 and 10.1.2 and newer include fixes for this vulnerability.  If you are using version 7 or 8 you are encouraged to upgrade to a newer release.\n\n### Workarounds\n\n#### Patch your library\n\nManually patch your library to create null objects for both `languages` and `aliases`:\n\n```js\nconst HLJS = function(hljs) {\n  // ...\n  var languages = Object.create(null);\n  var aliases = Object.create(null);\n```\n\n#### Filter out bad data from end users:\n\nFilter the language names that users are allowed to inject into your HTML to guarantee they are valid.\n\n### References\n\n* [What is Prototype Pollution?](https://codeburst.io/what-is-prototype-pollution-49482fc4b638)\n* https://github.com/highlightjs/highlight.js/pull/2636\n\n### For more information\n\nIf you have any questions or comments about this advisory:\n\n* Please file an issue against [highlight.js](https://github.com/highlightjs/highlight.js/issues/)",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:N/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "highlight.js"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "9.18.2"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "npm",
      "name" : "highlight.js"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "10.0.0"
      }, {
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      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/highlightjs/highlight.js/security/advisories/GHSA-vfrc-7r7c-w9mx"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2020-26237"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/highlightjs/highlight.js/pull/2636"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/highlightjs/highlight.js/commit/7241013ae011a585983e176ddc0489a7a52f6bb0"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/highlightjs/highlight.js"
  }, {
    "type" : "WEB",
    "url" : "https://lists.debian.org/debian-lts-announce/2020/12/msg00041.html"
  }, {
    "type" : "WEB",
    "url" : "https://www.npmjs.com/package/highlight.js"
  }, {
    "type" : "WEB",
    "url" : "https://www.oracle.com/security-alerts/cpujul2022.html"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-471" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2020-11-24T22:56:50Z",
    "nvd_published_at" : "2020-11-24T23:15:00Z"
  }
}