CVE-2021-22863: Improper access control in GitHub Enterprise Server leading to unauthorized changes to maintainer permissions on pull requests

Severity: high (CVSS 8.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.0% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-03-03 · updated 2026-06-17
Weakness: CWE-285

Description

An improper access control vulnerability was identified in the GitHub Enterprise Server GraphQL API that allowed authenticated users of the instance to modify the maintainer collaboration permission of a pull request without proper authorization. By exploiting this vulnerability, an attacker would be able to gain access to head branches of pull requests opened on repositories of which they are a maintainer. Forking is disabled by default for organization owned private repositories and would prevent this vulnerability. Additionally, branch protections such as required pull request reviews or status checks would prevent unauthorized commits from being merged without further review or validation. This vulnerability affected all versions of GitHub Enterprise Server since 2.12.22 and was fixed in versions 2.20.24, 2.21.15, 2.22.7 and 3.0.1. This vulnerability was reported via the GitHub Bug Bounty program.

Affected products

Github: from 2.12.22 before 2.20.24; from 2.21.0 before 2.21.15; from 2.22.0 before 2.22.7; from 3.0.0 before 3.0.1 — fixed in 2.20.24, 2.21.15, 2.22.7, 3.0.1

How to fix

Upgrade to a fixed version: Github 2.20.24, 2.21.15, 2.22.7, 3.0.1. Check the vendor advisory for mitigations.

References

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