CVE-2026-103620: CWE-862 Missing Authorization in GitHub Enterprise Server
Description
CVE-2026-103620 is a missing authorization vulnerability in GitHub Enterprise Server that allowed repository collaborators with write access to delete the current default branch via the GraphQL API. This could cause an attacker-controlled branch to become the new default, bypassing pull-request review requirements in certain repository configurations. The issue affected multiple supported versions in the 3.18 to 3.22 series and was fixed in specific patch releases.
CVSS v4.0
Score 6.0medium
Affected software
GitHub
Enterprise Server
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
This vulnerability involves missing authorization checks in GitHub Enterprise Server's GraphQL API, enabling repository collaborators with write permissions to delete the default branch. In repositories requiring pull-request reviews but lacking branch deletion restrictions, this allowed bypassing review requirements by replacing the default branch with an attacker-controlled branch. The vulnerability impacted versions in the 3.18, 3.19, 3.20, 3.21, and 3.22 series and was addressed in versions 3.18.16, 3.19.13, 3.20.9, 3.21.7, and 3.22.2.
Potential Impact
An attacker with write access to a repository could delete the default branch and set an attacker-controlled branch as the new default. This bypassed pull-request review requirements in affected repositories, causing fresh clones and API requests for the default branch to use potentially malicious content. This could undermine code integrity and trust in the repository's content.
Mitigation Recommendations
The vulnerability has been fixed in GitHub Enterprise Server versions 3.18.16, 3.19.13, 3.20.9, 3.21.7, and 3.22.2. Users should upgrade to these or later versions to remediate the issue. No additional mitigation steps are indicated by the vendor advisory.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_P
- Date Reserved
- 2026-09-30T23:02:34.862Z
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6ac546312cdf04f656d49cb9
Added to database: 10/06/2026, 19:04:17 UTC
Last enriched: 10/06/2026, 23:04:04 UTC
Last updated: 10/06/2026, 23:04:04 UTC
Views: 9
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