CVE-2020-26237: Highlight.js Prototype Pollution Vulnerability

{
  "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"
      }, {
        "fixed" : "10.1.2"
      } ]
    } ]
  } ],
  "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"
  }
}