CVE-2020-26237

Description

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.

Status

Show unmaintained releases

Package	Ubuntu Release	Status
highlight.js	26.04 LTS resolute	Not affected
	25.10 questing	Not affected
	25.04 plucky	Ignored end of life, was needs-triage
	24.10 oracular	Ignored end of life, was needs-triage
	24.04 LTS noble	Not affected
	23.10 mantic	Ignored end of life, was needs-triage
	23.04 lunar	Ignored end of life, was needs-triage
	22.10 kinetic	Ignored end of life, was needs-triage
	22.04 LTS jammy	Not affected
	21.10 impish	Ignored end of life
	21.04 hirsute	Ignored end of life
	20.10 groovy	Ignored end of life
	20.04 LTS focal	Fixed 9.12.0+dfsg1-5ubuntu0.1~esm1
	18.04 LTS bionic	Fixed 9.12.0+dfsg1-4ubuntu0.1~esm1
	16.04 LTS xenial	Fixed 8.2+ds-4ubuntu0.1~esm1
	14.04 LTS trusty	Not in release

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Severity score breakdown

Parameter	Value
Base score	5.8 · Medium
Attack vector	Network
Attack complexity	High
Privileges required	Low
User interaction	Required
Scope	Changed
Confidentiality	None
Integrity impact	High
Availability impact	None
Vector	CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:N/I:H/A:N

References

Related Ubuntu Security Notices (USN)

USN-8276-1
Highlight.js vulnerability
19 May 2026