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.

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History

Wed, 22 Apr 2026 00:00:00 +0000

Type Values Removed Values Added
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.
Title Incorrect Regular Expression vulnerability in GitHub Enterprise Server allowed unauthorized access to user accounts via OAuth callback URL validation bypass
Weaknesses CWE-185
References
Metrics cvssV4_0

{'score': 7.5, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N'}


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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_P

Published:

Updated: 2026-04-21T22:12:45.356Z

Reserved: 2026-03-16T17:48:03.040Z

Link: CVE-2026-4296

cve-icon Vulnrichment

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cve-icon NVD

Status : Received

Published: 2026-04-21T23:16:21.807

Modified: 2026-04-21T23:16:21.807

Link: CVE-2026-4296

cve-icon Redhat

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cve-icon OpenCVE Enrichment

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Weaknesses