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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.

PUBLISHED Reserved 2026-03-16 | Published 2026-04-21 | Updated 2026-04-22 | Assigner GitHub_P




HIGH: 7.5CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Problem types

CWE-185 Incorrect Regular Expression

Product status

Default status
affected

3.14.0 (semver)
affected

3.15.0 (semver)
affected

3.16.0 (semver)
affected

3.17.0 (semver)
affected

3.18.0 (semver)
affected

3.19.0 (semver)
affected

3.20.0 (semver) before 3.20.1
affected

Credits

ahacker1 finder

hacktron finder

References

docs.github.com/...nterprise-server@3.14/admin/release-notes release-notes

docs.github.com/...nterprise-server@3.15/admin/release-notes release-notes

docs.github.com/...nterprise-server@3.16/admin/release-notes release-notes

docs.github.com/...nterprise-server@3.17/admin/release-notes release-notes

docs.github.com/...nterprise-server@3.18/admin/release-notes release-notes

docs.github.com/...nterprise-server@3.19/admin/release-notes release-notes

docs.github.com/...nterprise-server@3.20/admin/release-notes release-notes

cve.org (CVE-2026-4296)

nvd.nist.gov (CVE-2026-4296)

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