CVE-2026-4296 Auth bypass in Enterprise Server

High 7.5 Published 21 Apr 2026 Updated 22 Apr 2026

Attackers can bypass OAuth callback validation to steal authorization codes and gain unauthorized access to user accounts.

Exploited in the wild: Not known
Login needed: Any signed-in user
Attackable: Over the internet
Victim action needed: A user has to click or open something
Fix: None listed

What is CVE-2026-4296?

CVE-2026-4296 is a high-severity authentication bypass vulnerability in Github Enterprise Server, published on 21 Apr 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

Official 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.

Weakness: CWE-185

Which versions are affected by CVE-2026-4296?

It affects 1 product.

Products include Github Enterprise Server.

How do I fix CVE-2026-4296?

No fix has been published for CVE-2026-4296 yet. Limit exposure of the affected software until one is available.

Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.

Is CVE-2026-4296 being exploited?

There is no known exploitation of CVE-2026-4296 in the wild and no public exploit code.

All Github Enterprise Server vulnerabilities

Sources

Also known as GHSA-mcp7-23p7-2v34.