CVE-2026-77912Stored cross-site scripting vulnerability in GitHub Enterprise Server allowed HTML attribute injection via the Markdown rendering pipeline
Updated under an hour ago ()
Does this affect you?
It affects GitHub Enterprise Server. Add what you run to find out whether that includes you.
No exploitation reported and no EPSS estimate yet.
Do this next
Free account, 1 product
A stored cross-site scripting (XSS) vulnerability was identified in GitHub Enterprise Server that allowed an authenticated attacker to inject arbitrary HTML attributes into rendered Markdown because the Markdown rendering pipeline rewrote quote characters in already-sanitized HTML without re-sanitizing the result. Crafted Markdown could abuse same-origin JavaScript gadgets to bypass Content Security Policy and gain control of the page DOM when viewed by another user. Successful exploitation could allow an attacker to read content visible to the victim, extract embedded CSRF tokens, perform state-changing actions as the victim, and exfiltrate data through same-origin writes. The payload could also propagate to repositories and organizations where the victim had write access. This vulnerability affected supported GitHub Enterprise Server releases in the 3.17, 3.18, 3.19, 3.20, 3.21, and 3.22 series and was fixed in versions 3.22.1, 3.21.6, 3.20.8, 3.19.12, 3.18.15, and 3.17.21. This vulnerability was reported via the GitHub Bug Bounty program.
- CVSS
- 7.4 HIGH (v4.0, CNA)CVSS:4.0/AV:N/AC:H/AT:N/PR:L/UI:P/VC:H/VI:H/VA:N/SC:L/SI:L/SA:N/AU:Y
- Weakness (CWE)
- CWE-79
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- GitHub_P
- NVD analysis
- Analyzed
- Record last updated
- Sep 23, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
GitHub Enterprise Server github:enterprise_server (from the name) | from 3.17.0 before 3.17.*; fixed at 3.17.21; from 3.18.0 before 3.18.*; fixed at 3.18.15; from 3.19.0 before 3.19.*; fixed at 3.19.12; from 3.20.0 before 3.20.*; fixed at 3.20.8; from 3.21.0 before 3.21.*; fixed at 3.21.6; from 3.22.0 before 3.22.*; fixed at 3.22.1 | CNA record |
github enterprise_server github:enterprise_server | from 3.17.0 before 3.17.21; from 3.18.0 before 3.18.15; from 3.19.0 before 3.19.12; from 3.20.0 before 3.20.8; from 3.21.0 before 3.21.6; from 3.22.0 before 3.22.1 | NVD |
References
- https://docs.github.com/en/enterprise-server@3.17/admin/release-notes#3.17.21release-notes, vendor-advisory
- https://docs.github.com/en/enterprise-server@3.18/admin/release-notes#3.18.15release-notes, vendor-advisory
- https://docs.github.com/en/enterprise-server@3.19/admin/release-notes#3.19.12release-notes, vendor-advisory
- https://docs.github.com/en/enterprise-server@3.20/admin/release-notes#3.20.8release-notes, vendor-advisory
- https://docs.github.com/en/enterprise-server@3.21/admin/release-notes#3.21.6release-notes, vendor-advisory
- https://docs.github.com/en/enterprise-server@3.22/admin/release-notes#3.22.1release-notes, vendor-advisory
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.