Missing authorization in GitHub Enterprise Server allowed repository writers to replace default branches via GraphQL
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.
CVE-2026-103620
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-103620
Enterprise Server
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"vendor": "GitHub",
"product": "Enterprise Server",
"versions": [
{
"status": "affected",
"changes": [
{
"at": "3.18.16",
"status": "unaffected"
}
],
"version": "3.18.0",
"lessThan": "3.18.*",
"versionType": "semver"
},
{
"status": "affected",
"changes": [
{
"at": "3.19.13",
"status": "unaffected"
}
],
"version": "3.19.0",
"lessThan": "3.19.*",
"versionType": "semver"
},
{
"status": "affected",
"changes": [
{
"at": "3.20.9",
"status": "unaffected"
}
],
"version": "3.20.0",
"lessThan": "3.20.*",
"versionType": "semver"
},
{
"status": "affected",
"changes": [
{
"at": "3.21.7",
"status": "unaffected"
}
],
"version": "3.21.0",
"lessThan": "3.21.*",
"versionType": "semver"
},
{
"status": "affected",
"changes": [
{
"at": "3.22.2",
"status": "unaffected"
}
],
"version": "3.22.0",
"lessThan": "3.22.*",
"versionType": "semver"
}
],
"defaultStatus": "unknown"
}
]- Related CVEs
- CVE-2026-103620
Source reference:
/cveMetadata/cveId
Publisher severity
medium
Source reference: /containers/cna/metrics
- Event
- #11994 · Revision 1
- Added to Heist Feed
- Publisher date