XSS in GitHub Enterprise Server
CVE-2026-2266
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.
Vulnerability class: XSS (Cross-Site Scripting)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N.
EPSS exploit prediction
EPSS: 0.002 (6.3th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 6th percentile — 6.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: 0.000
Affected products
- GitHub Enterprise Server — versions 3.18.0, 3.19.0
- GitHub Enterprise Server
Weakness classification (CWE)
References
- docs.github.com/en/enterprise-server@3.18/admin/release-notes (release-notes, Release Notes)
- docs.github.com/en/enterprise-server@3.19/admin/release-notes (release-notes, Release Notes)
Frequently asked questions
- What is CVE-2026-2266?
- CVE-2026-2266 is a medium-severity vulnerability in GitHub Enterprise Server, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2026-03-10.
- How severe is CVE-2026-2266?
- Medium severity. CVSS v3 base score is 5.4 out of 10.