CVE-2026-77912
published 2026-09-22CVE-2026-77912: A stored cross-site scripting (XSS) vulnerability was identified in GitHub Enterprise Server that allowed an authenticated attacker to inject arbitrary HTML…
PriorityP429medium5.4CVSS 3.1
AVNACLPRLUIRSCCLILAN
EPSS
0.21%
9.7th percentile
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.
Affected
12 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| github | enterprise_server | >= 3.17.0 < 3.17.* | 3.17.* |
| github | enterprise_server | >= 3.17.0 < 3.17.21 | 3.17.21 |
| github | enterprise_server | >= 3.18.0 < 3.18.* | 3.18.* |
| github | enterprise_server | >= 3.18.0 < 3.18.15 | 3.18.15 |
| github | enterprise_server | >= 3.19.0 < 3.19.* | 3.19.* |
| github | enterprise_server | >= 3.19.0 < 3.19.12 | 3.19.12 |
| github | enterprise_server | >= 3.20.0 < 3.20.* | 3.20.* |
| github | enterprise_server | >= 3.20.0 < 3.20.8 | 3.20.8 |
| github | enterprise_server | >= 3.21.0 < 3.21.* | 3.21.* |
| github | enterprise_server | >= 3.21.0 < 3.21.6 | 3.21.6 |
| github | enterprise_server | >= 3.22.0 < 3.22.* | 3.22.* |
| github | enterprise_server | >= 3.22.0 < 3.22.1 | 3.22.1 |
CVSS provenance
nvdv3.15.4MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
nvdv4.07.4HIGHCVSS: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
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VulDB
GitHub Enterprise Server up to 3.22.0 Markdown Rendering cross site scripting
vuldb·2026-09-22·CVSS 7.4
CVE-2026-77912 [HIGH] GitHub Enterprise Server up to 3.22.0 Markdown Rendering cross site scripting
A vulnerability identified as problematic has been detected in GitHub Enterprise Server up to 3.22.0. Affected by this issue is some unknown functionality of the component Markdown Rendering. This manipulation causes cross site scripting.
The identification of this vulnerability is CVE-2026-77912. It is possible to initiate the attack remotely. There is no exploit available.
You should upgrade the affected component.
GHSA
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 t
ghsa_unreviewed·2026-09-22
CVE-2026-77912 [HIGH] CWE-79 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 t
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 vulnerabil
No detection rules found.
No public exploits indexed.
No writeups or analysis indexed.
https://docs.github.com/en/[email protected]/admin/release-notes#3.17.21https://docs.github.com/en/[email protected]/admin/release-notes#3.18.15https://docs.github.com/en/[email protected]/admin/release-notes#3.19.12https://docs.github.com/en/[email protected]/admin/release-notes#3.20.8https://docs.github.com/en/[email protected]/admin/release-notes#3.21.6https://docs.github.com/en/[email protected]/admin/release-notes#3.22.1
2026-09-22
Published