Vulnerability · Published Oct 6, 2026 · Assigned by GitHub_P
CVE-2026-103620Missing authorization in GitHub Enterprise Server allowed repository writers to replace default branches via GraphQL
Medium 6.0
In plain English
A medium-severity missing authorization in Enterprise Server from GitHub. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 43% of all known vulnerabilities).
Official description
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.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| GitHub | Enterprise Server | 3.18.0 – before 3.18.*3.19.0 – before 3.19.*3.20.0 – before 3.20.*3.21.0 – before 3.21.*3.22.0 – before 3.22.* |
Weakness: CWE-862 · Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
References
- https://docs.github.com/en/enterprise-server@3.18/admin/release-notes#3.18.16 release-notes
- https://docs.github.com/en/enterprise-server@3.19/admin/release-notes#3.19.13 release-notes
- https://docs.github.com/en/enterprise-server@3.20/admin/release-notes#3.20.9 release-notes
- https://docs.github.com/en/enterprise-server@3.21/admin/release-notes#3.21.7 release-notes
- https://docs.github.com/en/enterprise-server@3.22/admin/release-notes#3.22.2 release-notes