CVE-2026-1999

An incorrect authorization vulnerability was identified in GitHub Enterprise Server that allowed an attacker to merge their own pull request into a repository without having push access by exploiting an authorization bypass in the enable_auto_merge mutation for pull requests. This issue only affected repositories that allow forking as the attack relies on opening a pull request from an attacker-controlled fork into the target repository. Exploitation was only possible in specific scenarios. It required a clean pull request status and only applied to branches without branch protection rules enabled. This vulnerability affected GitHub Enterprise Server versions prior to 3.19.2, 3.18.5, and 3.17.11, and was fixed in versions 3.19.2, 3.18.5, and 3.17.11. This vulnerability was reported via the GitHub Bug Bounty program.

Affected products

Github Enterprise Server

Github Enterprise Server

< 3.17.11, 3.18.5, 3.19.2

CVSS 4.0

7.1 HIGH

CVSS 3.1

6.5 MEDIUM

EPSS

0.3% (24th percentile)

Weakness

CWE-863

NVD status

Modified

Published

2026-02-18

Attack patterns

CAPEC-233