Vulnerability in GitHub Enterprise Server
CVE-2026-4296
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 · last modified .
CVSS v3 metric
CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.007 (53.6th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 54th percentile — 53.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.007 · change: +0.003
Affected products
- GitHub Enterprise Server — versions 3.14.0, 3.15.0, 3.16.0
- GitHub Enterprise Server — versions 3.20.0
Weakness classification (CWE)
References
- docs.github.com/en/enterprise-server@3.14/admin/release-notes (release-notes, Release Notes, Vendor Advisory)
- docs.github.com/en/enterprise-server@3.15/admin/release-notes (release-notes, Release Notes, Vendor Advisory)
- docs.github.com/en/enterprise-server@3.16/admin/release-notes (release-notes, Release Notes, Vendor Advisory)
- docs.github.com/en/enterprise-server@3.17/admin/release-notes (release-notes, Release Notes, Vendor Advisory)
- docs.github.com/en/enterprise-server@3.18/admin/release-notes (release-notes, Release Notes, Vendor Advisory)
- docs.github.com/en/enterprise-server@3.19/admin/release-notes (release-notes, Release Notes, Vendor Advisory)
- docs.github.com/en/enterprise-server@3.20/admin/release-notes (release-notes, Release Notes, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-4296?
- CVE-2026-4296 is a high-severity vulnerability in GitHub Enterprise Server, classified under Incorrect Regular Expression. CVSS score: 8.8/10. Published 2026-04-21.
- How severe is CVE-2026-4296?
- High severity. CVSS v3 base score is 8.8 out of 10.