CVE-2026-2266

Improper neutralization of input vulnerability was identified in GitHub Enterprise Server that allowed cross-site scripting via task list content and enabled arbitrary HTML injection

State: Published
Severity: 7.4 High
Published: Mar 10, 2026
Updated: Mar 11, 2026
Reserved: Feb 9, 2026

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Description

An improper neutralization of input vulnerability was identified in GitHub Enterprise Server that allowed DOM-based cross-site scripting via task list content. The task list content extraction logic did not properly re-encode browser-decoded text nodes before rendering, allowing user-supplied HTML to be injected into the page. An authenticated attacker could craft malicious task list items in issues or pull requests to execute arbitrary scripts in the context of another user's browser session. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.20 and was fixed in versions 3.18.6 and 3.19.3. This vulnerability was reported via the GitHub Bug Bounty program.

Scores

CVSS	Score	Vector	Source
4.0	7.4 High	CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N	GitHub_P

Weaknesses

CWE-79 Improper neutralization of input during web page generation ('cross-site scripting')

Affected Products

Product	Versions
Enterprise ServerGitHub	3.18.0 through 3.18.5Affectedfrom 3.18.6Not affected 3.19.0 through 3.19.2Affectedfrom 3.19.3Not affected

References

https://docs.github.com/en/enterprise-server@3.18/admin/release-notes#3.18.6release-notes
https://docs.github.com/en/enterprise-server@3.19/admin/release-notes#3.19.3release-notes

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