GHSA-VFRC-7R7C-W9MX

Vulnerability from github – Published: 2020-11-24 22:58 – Updated: 2022-10-20 13:52
VLAI?
Summary
Prototype Pollution in highlight.js
Details

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:

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

For more information

If you have any questions or comments about this advisory:

Severity ?
5.8 (Medium)
CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:N/I:H/A:N
Show details on source website
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{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "highlight.js"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "9.18.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "highlight.js"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "10.0.0"
            },
            {
              "fixed": "10.1.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2020-26237"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-471"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2020-11-24T22:56:50Z",
    "nvd_published_at": "2020-11-24T23:15:00Z",
    "severity": "MODERATE"
  },
  "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\u0027s 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/)",
  "id": "GHSA-vfrc-7r7c-w9mx",
  "modified": "2022-10-20T13:52:50Z",
  "published": "2020-11-24T22:58:41Z",
  "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"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:N/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Prototype Pollution in highlight.js"
}


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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



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