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CVE-2026-4296PATCHED
github · enterprise server

Incorrect Regular Expression vulnerability in GitHub Enterprise Server allowed unauthorized access to user accounts via OAuth callback URL validation bypass

Description

An incorrect regular expression vulnerability was identified in GitHub Enterprise Server that allowed an attacker to bypass OAuth redirect URI validation. An attacker with knowledge of a first-party OAuth application's registered callback URL could craft a malicious authorization link that, when clicked by a victim, would redirect the OAuth authorization code to an attacker-controlled domain. This could allow the attacker to gain unauthorized access to the victim's account with the scopes granted to the OAuth application. 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, 3.14.26. This vulnerability was reported via the GitHub Bug Bounty program.

Affected Products

VendorProductVersions
githubenterprise server3.14.0, 3.15.0, 3.16.0, 3.17.0, 3.18.0, 3.19.0, 3.20.0

Also Affects

Downstream vendors/products affected by this vulnerability

VendorProductSourceConfidence
microsoftgithub enterprisecert_advisory90%

References

  • https://docs.github.com/en/enterprise-server@3.14/admin/release-notes#3.14.26(release-notes)
  • https://docs.github.com/en/enterprise-server@3.15/admin/release-notes#3.15.21(release-notes)
  • https://docs.github.com/en/enterprise-server@3.16/admin/release-notes#3.16.17(release-notes)
  • https://docs.github.com/en/enterprise-server@3.17/admin/release-notes#3.17.14(release-notes)
  • https://docs.github.com/en/enterprise-server@3.18/admin/release-notes#3.18.8(release-notes)
  • https://docs.github.com/en/enterprise-server@3.19/admin/release-notes#3.19.5(release-notes)
  • https://docs.github.com/en/enterprise-server@3.20/admin/release-notes#3.20.1(release-notes)

Related News (2 articles)

Tier B
BSI Advisories11d ago
[NEU] [hoch] Microsoft GitHub Enterprise: Mehrere Schwachstellen
→ No new info (linked only)
Tier C
VulDB11d ago
CVE-2026-4296 | GitHub Enterprise Server up to 3.20.0 incorrect regex
→ No new info (linked only)
CISA KEV❌ No
Actively exploited❌ No
Patch available
3.20.1
CWECWE-185
PublishedApr 21, 2026
Last enriched11d agov2
Trending Score9
Source articles2
Independent2
Info Completeness8/14
Missing: cvss, epss, kev, exploit, iocs, mitre_attack

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Related CVEs (5)

CRITICALCVE-2026-3854
Remote code execution via git push option injection in GitHub Enterprise Server
Trending: 66
HIGHCVE-2026-4821EXP
Proxy configuration command injection vulnerability found in GitHub Enterprise Server Management Console configuration API
Trending: 14
NONECVE-2026-5921
Server-Side Request Forgery in GitHub Enterprise Server allowed extraction of sensitive environment variables via timing side-channel attack
Trending: 9
NONECVE-2026-5512EXP
Improper authorization vulnerability in GitHub Enterprise Server allowed disclosure of private repository names via mobile upload policy API
Trending: 9
NONECVE-2026-5845
Improper authorization fallback allows scoped user-to-server token installation escape in GitHub Enterprise Server
Trending: 9

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Verification

State: unverified
Confidence: 0%

Vulnerability Timeline

CVE Published
Apr 21, 2026
Discovered by ZDM
Apr 21, 2026
Updated: severity
Apr 22, 2026
Patch Available
Apr 22, 2026

Version History

v2
Last enriched 11d ago
v2Tier C11d ago

Updated severity to CRITICAL and corrected exploit availability status.

severity
via VulDB
v111d ago

Initial creation