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

Medium 6.5 Published 3 Mar 2021 Updated 3 Aug 2024

Authenticated users can gain unauthorized write access to forkable repositories via crafted pull requests and API calls.

Exploited in the wild: Not known
Login needed: Any signed-in user
Attackable: Over the internet
Victim action needed: Not needed
Fix: None listed

What is CVE-2021-22861?

CVE-2021-22861 is a medium-severity missing authorization vulnerability in GitHub Enterprise Server, published on 3 Mar 2021. Any signed-in user can exploit it over the network, with no action from the victim.

Official 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.

Weakness: CWE-285

Which versions are affected by CVE-2021-22861?

It affects 1 product.

Products include Github Github.

How do I fix CVE-2021-22861?

No fix has been published for CVE-2021-22861 yet. Limit exposure of the affected software until one is available.

Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.

Is CVE-2021-22861 being exploited?

There is no known exploitation of CVE-2021-22861 in the wild and no public exploit code.

Sources

Also known as GHSA-x87g-4c45-mvv5.