CVE-2026-77912
What it is
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.
At a glance
- Exploitability
- Can be exploited over the network with a low-privilege account, but needs a user to act. High risk of data exposure, data tampering.
- Exploit odds
- 0.2% chance of exploitation in the next 30 days (EPSS).
- Fix
- A patch, advisory or fixed version is referenced. Upgrade or apply it.
Timeline
- ReservedThe CVE id was reserved by its CNA
- PublishedDisclosed publicly on CVE.org and NVD
- Last updatedMost recent change to the record
Why it ranks here
- Exploited in the wild: no, CISA does not list it.
- Exploit odds: 0.2% in the next 30 days (EPSS).
- Severity: 7.4 HIGH (CVSS).
- Fix: a patch or advisory is linked.
Details
- Published
- Last modified
- Exploit probability
- 0.2% · EPSS, next 30 days
- Weakness
- CWE-79 · Cross-site scripting
- Record status
- Analyzed
Affected
- GitHub Enterprise Server < 3.17.21
- GitHub Enterprise Server < 3.18.15
- GitHub Enterprise Server < 3.19.12
- GitHub Enterprise Server < 3.20.8
- GitHub Enterprise Server < 3.21.6
- GitHub Enterprise Server < 3.22.1
Attack profile CVSS 4.0 · 7.4
- Attack vector
- Network
- Complexity
- High
- Attack requirements
- None
- Privileges needed
- Low
- User interaction
- Passive
- Confidentiality
- High
- Integrity
- High
- Availability
- None
Raw vector
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:Y/R:X/V:X/RE:X/U:X
Is it in your code?
Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.
Read https://cve-list.com/agent/cve/CVE-2026-77912.md and follow it. Check whether this project is affected by CVE-2026-77912. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.
Fix and advisories
- https://docs.github.com/en/[email protected]/admin/release-notes#3.17.21
- https://docs.github.com/en/[email protected]/admin/release-notes#3.18.15
- https://docs.github.com/en/[email protected]/admin/release-notes#3.19.12
- https://docs.github.com/en/[email protected]/admin/release-notes#3.20.8
- https://docs.github.com/en/[email protected]/admin/release-notes#3.21.6
- https://docs.github.com/en/[email protected]/admin/release-notes#3.22.1
References
- https://docs.github.com/en/[email protected]/admin/release-notes#3.17.21
- https://docs.github.com/en/[email protected]/admin/release-notes#3.18.15
- https://docs.github.com/en/[email protected]/admin/release-notes#3.19.12
- https://docs.github.com/en/[email protected]/admin/release-notes#3.20.8
- https://docs.github.com/en/[email protected]/admin/release-notes#3.21.6
- https://docs.github.com/en/[email protected]/admin/release-notes#3.22.1