A missing authorization vulnerability was identified in GitHub Enterprise Server that allowed a repository collaborator with write access to delete the current default branch through the GraphQL API and cause an attacker-controlled branch to become the new default. In repositories that required pull-request review but did not restrict branch deletion, this bypassed the review requirement and caused fresh clones and default-branch API requests to use attacker-controlled content. This vulnerability affected supported GitHub Enterprise Server releases in the 3.18, 3.19, 3.20, 3.21, and 3.22 series and was fixed in versions 3.18.16, 3.19.13, 3.20.9, 3.21.7, and 3.22.2. This vulnerability was reported via the GitHub Bug Bounty program.
Fix
Patch, vendor advisory and mitigation references on NVD 5
- https://docs.github.com/en/[email protected]/admin/release-notes#3.18.16 Release Notes, Vendor Advisory
- https://docs.github.com/en/[email protected]/admin/release-notes#3.19.13 Release Notes, Vendor Advisory
- https://docs.github.com/en/[email protected]/admin/release-notes#3.20.9 Release Notes, Vendor Advisory
- https://docs.github.com/en/[email protected]/admin/release-notes#3.21.7 Release Notes, Vendor Advisory
- https://docs.github.com/en/[email protected]/admin/release-notes#3.22.2 Release Notes, Vendor Advisory
Every line above is quoted from NVD, CISA, Microsoft, the vendor's own advisory or DISA; nothing is generated.
Change history 1
- First seenCVSS 6.0 · githubNVD modified 2026-10-20 19:33
Affected (CPE criteria) 1
cpe:2.3:a:github:enterprise_server:*:*:*:*:*:*:*:*
References 5
- https://docs.github.com/en/[email protected]/admin/release-notes#3.18.16 Release Notes, Vendor Advisory
- https://docs.github.com/en/[email protected]/admin/release-notes#3.19.13 Release Notes, Vendor Advisory
- https://docs.github.com/en/[email protected]/admin/release-notes#3.20.9 Release Notes, Vendor Advisory
- https://docs.github.com/en/[email protected]/admin/release-notes#3.21.7 Release Notes, Vendor Advisory
- https://docs.github.com/en/[email protected]/admin/release-notes#3.22.2 Release Notes, Vendor Advisory