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CVE-2026-5845

Improper authorization fallback allows scoped user-to-server token installation escape in GitHub Enterprise Server

Published: Apr 21, 2026Updated: Apr 29, 2026 Sources: CVE List NVDCWE-639
NVD MITRE
9.6CVSSCRITICAL
EPSS Score
0.2%
Top 87.5%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available

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.

CVSS Vector Breakdown

AV:NAC:LPR:LUI:NS:CC:HI:HA:N
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:LPrivileges Required
Low
UI:NUser Interaction
None
Scope
S:CScope
Changed
Impact
C:HConfidentiality
High
I:HIntegrity
High
A:NAvailability
None
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Weaknesses

CWE-639

Affected Products

Enterprise ServerGitHubDevTools & CI
enterprise servergithubDevTools & CI
githubcommercialUSDevTools & CIaka github

Attack Graph

Products CVE Techniques Tactics

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Exploitability

Official Patch Available

MITRE ATT&CK

1 technique
Initial Access
View detailed technique mapping

References

https://docs.github.com/en/enterprise-server@3.20/admin/release-notes#3.20.1
docs.github.com
https://docs.github.com/en/enterprise-server@3.19/admin/release-notes#3.19.5
docs.github.com
https://docs.github.com/en/enterprise-server@3.18/admin/release-notes#3.18.8
docs.github.com
and 4 more references View all →

Timeline

Published
Apr 21, 2026
Last Updated
Apr 29, 2026

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