GitHub Enterprise Server <3.21 Scoped Token Auth Flaw
CVE-2026-5845 Published on April 21, 2026
Improper authorization fallback allows scoped user-to-server token installation escape in GitHub Enterprise Server
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 Analysis
CVE-2026-5845 can be exploited with local system access, and requires small amount of user privileges. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity and availability.
Weakness Type
What is an Insecure Direct Object Reference / IDOR Vulnerability?
The system's authorization functionality does not prevent one user from gaining access to another user's data or record by modifying the key value identifying the data.
CVE-2026-5845 has been classified to as an Insecure Direct Object Reference / IDOR vulnerability or weakness.
Products Associated with CVE-2026-5845
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Affected Versions
GitHub Enterprise Server:- Version 3.20.0 and below 3.20.1 is affected.
- Version 3.19.0, <= 3.19.4 is affected.
- Version 3.18.0, <= 3.18.7 is affected.
- Version 3.17.0, <= 3.17.13 is affected.
- Version 3.16.0, <= 3.16.16 is affected.
- Version 3.15.0, <= 3.15.20 is affected.
- Version 3.14.0, <= 3.14.25 is affected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.