What’s Vulnerable › Vulnerabilities
CVE-2026-103620: Missing authorization in GitHub Enterprise Server allowed repository writers to replace default branches via GraphQL
- Severity: medium (CVSS 6.5 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 0.5% probability of exploitation in the next 30 days
- Public exploit or detection template: none known
- Published: 2026-10-06 · updated 2026-10-20
- Weakness: CWE-862
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
- GitHub Enterprise Server: from 3.18.0 before 3.18.16; from 3.19.0 before 3.19.13; from 3.20.0 before 3.20.9; from 3.21.0 before 3.21.7; from 3.22.0 before 3.22.2 — fixed in 3.18.16, 3.19.13, 3.20.9, 3.21.7, 3.22.2
How to fix
Upgrade to a fixed version: GitHub Enterprise Server 3.18.16, 3.19.13, 3.20.9, 3.21.7. Check the vendor advisory for mitigations.
References
- https://docs.github.com/en/enterprise-server@3.18/admin/release-notes#3.18.16
- https://docs.github.com/en/enterprise-server@3.19/admin/release-notes#3.19.13
- https://docs.github.com/en/enterprise-server@3.20/admin/release-notes#3.20.9
- https://docs.github.com/en/enterprise-server@3.21/admin/release-notes#3.21.7
- https://docs.github.com/en/enterprise-server@3.22/admin/release-notes#3.22.2
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