Auth bypass in GitHub Enterprise Server
CVE-2026-5845
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.
Vulnerability class: IDOR (Insecure Direct Object Reference)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 9.6 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N.
EPSS exploit prediction
EPSS: 0.005 (40.0th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 40th percentile — 40.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.005 · change: +0.002
Affected products
- GitHub Enterprise Server — versions 3.20.0, 3.19.0, 3.18.0
- GitHub Enterprise Server — versions 3.20.0
Weakness classification (CWE)
References
- docs.github.com/en/enterprise-server@3.20/admin/release-notes (Release Notes, Vendor Advisory)
- docs.github.com/en/enterprise-server@3.19/admin/release-notes (Release Notes, Vendor Advisory)
- docs.github.com/en/enterprise-server@3.18/admin/release-notes (Release Notes, Vendor Advisory)
- docs.github.com/en/enterprise-server@3.17/admin/release-notes (Release Notes, Vendor Advisory)
- docs.github.com/en/enterprise-server@3.16/admin/release-notes (Release Notes, Vendor Advisory)
- docs.github.com/en/enterprise-server@3.15/admin/release-notes (Release Notes, Vendor Advisory)
- docs.github.com/en/enterprise-server@3.14/admin/release-notes (Release Notes, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-5845?
- CVE-2026-5845 is a critical-severity vulnerability in GitHub Enterprise Server, classified under Authorization Bypass Through User-Controlled Key. CVSS score: 9.6/10. Published 2026-04-21.
- How severe is CVE-2026-5845?
- Critical severity. CVSS v3 base score is 9.6 out of 10.