Description
An improper authorization vulnerability in scoped user-to-server (ghu_) token authorization in GitHub Enterprise Server allows an authenticated attacker to access private repositories outside the intended installation scope, which can include write operations, via an authorization fallback that treated a revoked/deleted installation as a global installation context, which could be chained with token revocation timing and SSH push attribution to obtain and reuse a victim-scoped token. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.21 and was fixed in versions 3.20.1, 3.19.5, 3.18.8, 3.17.14, 3.16.17, 3.15.21, and 3.14.26. This vulnerability was reported via the GitHub Bug Bounty program.
Metrics
CVSS 3.1 9.6/10
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:NWeakness enumeration
Affected software
| Vendor | Product | Versions |
|---|---|---|
| GitHub | Enterprise Server | >= 3.20.0, < 3.20.1; >= 3.19.0, <= 3.19.4; >= 3.18.0, <= 3.18.7; >= 3.17.0, <= 3.17.13; >= 3.16.0, <= 3.16.16; >= 3.15.0, <= 3.15.20; >= 3.14.0, <= 3.14.25 |
References
- https://docs.github.com/en/enterprise-server@3.14/admin/release-notes#3.14.26Release Notes, Vendor Advisory
- https://docs.github.com/en/enterprise-server@3.15/admin/release-notes#3.15.21Release Notes, Vendor Advisory
- https://docs.github.com/en/enterprise-server@3.16/admin/release-notes#3.16.17Release Notes, Vendor Advisory
- https://docs.github.com/en/enterprise-server@3.17/admin/release-notes#3.17.14Release Notes, Vendor Advisory
- https://docs.github.com/en/enterprise-server@3.18/admin/release-notes#3.18.8Release Notes, Vendor Advisory
- https://docs.github.com/en/enterprise-server@3.19/admin/release-notes#3.19.5Release Notes, Vendor Advisory
- https://docs.github.com/en/enterprise-server@3.20/admin/release-notes#3.20.1Release Notes, Vendor Advisory
Timeline
- Published
- Apr 21, 2026
- Last modified
- Oct 26, 2026
- NVD status
- Analyzed