# CVE-2026-4296: An incorrect regular expression vulnerability was identified in GitHub Enterprise Server that allowed an attacker to…

Source: https://junglewise.ai/threats/cve-2026-4296-an-incorrect-regular-expression-vulnerability-was-identified-in  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-04-21  
License: CC BY 4.0 with a link back

CVE-2026-4296 · Severity: high · CVSS 8.8 · Published 2026-04-21

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.

Technologies: [GitHub Enterprise Server](https://junglewise.ai/threats/technologies/github-enterprise-server). Vendors: [GitHub](https://junglewise.ai/threats/vendors/github).

## Quick answers

**Is CVE-2026-4296 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-4296 being exploited in the wild.

**How severe is CVE-2026-4296?** High severity, with a CVSS score of 8.8, published 21 April 2026.

**Which products and versions are affected?** GitHub Enterprise Server. The advisory does not name versions.

**Is there a fix for CVE-2026-4296?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**Am I affected by CVE-2026-4296?** Check whether you run GitHub Enterprise Server. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Affected products

- GitHub Enterprise Server

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