CVE catalog

CVE-2020-26237

highlight.js affected and fixed versions

Highlight.js is a syntax highlighter written in JavaScript. Highlight.js versions before 9.18.2 and 10.1.2 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. 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.

Severity: Medium · CVSS 5.8CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:N/I:H/A:N
Published: Nov 23, 2020, 12:00:00 AM UTC
Source: [NVD] · [CVE record]
EPSS: 1.33% · Oct 27, 2026

Projects and upstream resources

[highlight.js][Source-reported homepage]

Reported versions and fixes

Each observation applies to its named package, distribution, and release. Distribution backports can fix a vulnerability while retaining an older upstream version number.

Distribution / release	Package	Version	Status	Source
Debiantrixie	highlight.js	`9.18.1+dfsg1-3`	FixedDistribution-reported fixed boundary	[CVE-2020-26237]
Debiantrixie	highlight.js	`9.18.5+dfsg1-2`	Fixed	[CVE-2020-26237]
Debiansid	highlight.js	`10.7.3+dfsg-6`	Fixed	[CVE-2020-26237]
Debiansid	highlight.js	`9.18.1+dfsg1-3`	FixedDistribution-reported fixed boundary	[CVE-2020-26237]
Debianforky	highlight.js	`10.7.3+dfsg-6`	Fixed	[CVE-2020-26237]
Debianforky	highlight.js	`9.18.1+dfsg1-3`	FixedDistribution-reported fixed boundary	[CVE-2020-26237]
Debianbookworm	highlight.js	`9.18.1+dfsg1-3`	FixedDistribution-reported fixed boundary	[CVE-2020-26237]
Debianbookworm	highlight.js	`9.18.5+dfsg1-2`	Fixed	[CVE-2020-26237]

Showing 8 fix observations. All 11 observations, including unknown and conflicting reports, are available below.

Provider details and historical evidence

Distribution / release	Package	Version	Status	Source
Debianbookworm	highlight.js	`9.18.1+dfsg1-3`	FixedDistribution-reported fixed boundary	[CVE-2020-26237]
Debianbookworm	highlight.js	`9.18.5+dfsg1-2`	Fixed	[CVE-2020-26237]
Debianforky	highlight.js	`10.7.3+dfsg-6`	Fixed	[CVE-2020-26237]
Debianforky	highlight.js	`9.18.1+dfsg1-3`	FixedDistribution-reported fixed boundary	[CVE-2020-26237]
Debiansid	highlight.js	`10.7.3+dfsg-6`	Fixed	[CVE-2020-26237]
Debiansid	highlight.js	`9.18.1+dfsg1-3`	FixedDistribution-reported fixed boundary	[CVE-2020-26237]
Debiantrixie	highlight.js	`9.18.1+dfsg1-3`	FixedDistribution-reported fixed boundary	[CVE-2020-26237]
Debiantrixie	highlight.js	`9.18.5+dfsg1-2`	Fixed	[CVE-2020-26237]
Ubuntupro	highlight.js	`9.12.0+dfsg1-4ubuntu1`	UnknownSource applicability is not established	[UBUNTU-CVE-2020-26237]May 20, 2026, 4:04:20 PM UTC
Ubuntupro	highlight.js	`9.12.0+dfsg1-5`	UnknownSource applicability is not established	[UBUNTU-CVE-2020-26237]May 20, 2026, 4:04:20 PM UTC
Ubuntupro	highlight.js	`9.12.0+dfsg1-5ubuntu0.1~esm1`	UnknownSource applicability is not established	[UBUNTU-CVE-2020-26237]May 20, 2026, 4:04:20 PM UTC

Original provider fields

{
  "package_releases": [
    {
      "name": "highlight.js",
      "status": "fixed",
      "release": "sid",
      "version": "10.7.3+dfsg-6"
    },
    {
      "name": "highlight.js",
      "status": "fixed",
      "release": "forky",
      "version": "10.7.3+dfsg-6"
    },
    {
      "name": "highlight.js",
      "status": "fixed",
      "release": "trixie",
      "version": "9.18.5+dfsg1-2"
    },
    {
      "name": "highlight.js",
      "status": "fixed",
      "release": "bookworm",
      "version": "9.18.5+dfsg1-2"
    }
  ],
  "fixed_versions": [
    {
      "bug": 976446,
      "name": "highlight.js",
      "type": "source",
      "origin": null,
      "release": "sid",
      "urgency": "not yet assigned",
      "fixed_version": "9.18.1+dfsg1-3"
    },
    {
      "bug": 976446,
      "name": "highlight.js",
      "type": "source",
      "origin": null,
      "release": "forky",
      "urgency": "not yet assigned",
      "fixed_version": "9.18.1+dfsg1-3"
    },
    {
      "bug": 976446,
      "name": "highlight.js",
      "type": "source",
      "origin": null,
      "release": "trixie",
      "urgency": "not yet assigned",
      "fixed_version": "9.18.1+dfsg1-3"
    },
    {
      "bug": 976446,
      "name": "highlight.js",
      "type": "source",
      "origin": null,
      "release": "bookworm",
      "urgency": "not yet assigned",
      "fixed_version": "9.18.1+dfsg1-3"
    }
  ],
  "distribution_packages": [
    {
      "name": "highlight.js",
      "distro": "ubuntu",
      "ranges": [
        {
          "type": "ECOSYSTEM",
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "9.12.0+dfsg1-5ubuntu0.1~esm1"
            }
          ]
        }
      ],
      "release": "pro",
      "versions": [
        "9.12.0+dfsg1-4ubuntu1",
        "9.12.0+dfsg1-5"
      ],
      "ecosystem": "deb",
      "provider_url": "https://osv.dev/vulnerability/UBUNTU-CVE-2020-26237",
      "fixed_version": "9.12.0+dfsg1-5ubuntu0.1~esm1",
      "provider_source": "pypi",
      "provider_record_id": "UBUNTU-CVE-2020-26237",
      "provider_updated_at": "2026-05-20T16:04:20.867697717Z",
      "applicability_unknown": true
    }
  ]
}

[Debian bug #976446]

OpenFactory catalog packages

Matching against OpenFactory catalog package versions is in progress.

[Debian 12 (Bookworm)]

[highlight.js-doc]Unknown
Source package: [highlight.js]
Details (2)
- 9.18.5+dfsg1-2 · all · bookworm
  Fixed · Fixed: 9.18.1+dfsg1-3
  dsa · highlight.js · debian · bookworm; dsa · highlight.js · debian · 12
- 9.18.5+dfsg1-2 · all · bookworm
  Fixed · Fixed: 9.18.1+dfsg1-3
  dsa · highlight.js · debian · bookworm; dsa · highlight.js · debian · 12
[libjs-highlight.js]Unknown
Source package: [highlight.js]
Details (2)
- 9.18.5+dfsg1-2 · all · bookworm
  Fixed · Fixed: 9.18.1+dfsg1-3
  dsa · highlight.js · debian · bookworm; dsa · highlight.js · debian · 12
- 9.18.5+dfsg1-2 · all · bookworm
  Fixed · Fixed: 9.18.1+dfsg1-3
  dsa · highlight.js · debian · bookworm; dsa · highlight.js · debian · 12
[node-highlight.js]Unknown
Source package: [highlight.js]
Details (2)
- 9.18.5+dfsg1-2 · all · bookworm
  Fixed · Fixed: 9.18.1+dfsg1-3
  dsa · highlight.js · debian · bookworm; dsa · highlight.js · debian · 12
- 9.18.5+dfsg1-2 · all · bookworm
  Fixed · Fixed: 9.18.1+dfsg1-3
  dsa · highlight.js · debian · bookworm; dsa · highlight.js · debian · 12

[Debian 13 (Trixie)]

[highlight.js-doc]Unknown
Source package: [highlight.js]
Details (2)
- 9.18.5+dfsg1-2 · all · trixie
  Fixed · Fixed: 9.18.1+dfsg1-3
  dsa · highlight.js · debian · 13
- 9.18.5+dfsg1-2 · all · trixie
  Fixed · Fixed: 9.18.1+dfsg1-3
  dsa · highlight.js · debian · 13
[libjs-highlight.js]Unknown
Source package: [highlight.js]
Details (2)
- 9.18.5+dfsg1-2 · all · trixie
  Fixed · Fixed: 9.18.1+dfsg1-3
  dsa · highlight.js · debian · 13
- 9.18.5+dfsg1-2 · all · trixie
  Fixed · Fixed: 9.18.1+dfsg1-3
  dsa · highlight.js · debian · 13
[node-highlight.js]Unknown
Source package: [highlight.js]
Details (2)
- 9.18.5+dfsg1-2 · all · trixie
  Fixed · Fixed: 9.18.1+dfsg1-3
  dsa · highlight.js · debian · 13
- 9.18.5+dfsg1-2 · all · trixie
  Fixed · Fixed: 9.18.1+dfsg1-3
  dsa · highlight.js · debian · 13

Observed: Oct 23, 2026, 5:50:01 PM UTC

References

[CERT-Bund public advisories] · [Debian Security Tracker] · [FIRST EPSS] · [OSV Package Vulnerability Database] · [Red Hat security advisories and VEX]