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

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Summary

CVECVE-2026-5845
StatePUBLISHED
AssignerGitHub_P
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-21 23:16:22 UTC
Updated2026-04-29 12:30:18 UTC
DescriptionAn 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.

Risk And Classification

Primary CVSS: v4.0 7.2 HIGH from [email protected]

CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/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:X/R:X/V:X/RE:X/U:X

EPSS: 0.000130000 probability, percentile 0.021240000 (date 2026-04-22)

Problem Types: CWE-639 | CWE-639 CWE-639 Authorization bypass through User-Controlled key

VersionSourceTypeScoreSeverityVector
4.0[email protected]Secondary7.2HIGHCVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:N/SC:L/SI:L/SA:N/E:X/C...
4.0CNACVSS7.2HIGHCVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:N/SC:L/SI:L/SA:N
3.1[email protected]Primary9.6CRITICALCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N

CVSS v4.0 Breakdown

Attack Vector
Local
Attack Complexity
Low
Attack Requirements
Present
Privileges Required
Low
User Interaction
None
Confidentiality
High
Integrity
High
Availability
None
Sub Conf.
Low
Sub Integrity
Low
Sub Availability
None

CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/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:X/R:X/V:X/RE:X/U:X

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Github Enterprise Server All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA GitHub Enterprise Server affected 3.20.0 3.20.1 semver Not specified
CNA GitHub Enterprise Server affected 3.19.0 3.19.4 semver Not specified
CNA GitHub Enterprise Server affected 3.18.0 3.18.7 semver Not specified
CNA GitHub Enterprise Server affected 3.17.0 3.17.13 semver Not specified
CNA GitHub Enterprise Server affected 3.16.0 3.16.16 semver Not specified
CNA GitHub Enterprise Server affected 3.15.0 3.15.20 semver Not specified
CNA GitHub Enterprise Server affected 3.14.0 3.14.25 semver Not specified

References

ReferenceSourceLinkTags
docs.github.com/en/[email protected]/admin/release-notes [email protected] docs.github.com Release Notes, Vendor Advisory
docs.github.com/en/[email protected]/admin/release-notes [email protected] docs.github.com Release Notes, Vendor Advisory
docs.github.com/en/[email protected]/admin/release-notes [email protected] docs.github.com Release Notes, Vendor Advisory
docs.github.com/en/[email protected]/admin/release-notes [email protected] docs.github.com Release Notes, Vendor Advisory
docs.github.com/en/[email protected]/admin/release-notes [email protected] docs.github.com Release Notes, Vendor Advisory
docs.github.com/en/[email protected]/admin/release-notes [email protected] docs.github.com Release Notes, Vendor Advisory
docs.github.com/en/[email protected]/admin/release-notes [email protected] docs.github.com Release Notes, Vendor Advisory
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: ahacker1 (en)

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