CVE-2021-22861: An improper access control vulnerability was identified in GitHub Enterprise Server that allowed authenticated users of the instance to gain write acc...

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.

Metrics

CVSS 3.1

6.5/10

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N

EPSS Probability

0.92%

55.7th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-285

Affected Software

Vendor	Product	Versions
Github	Github	>= 2.4.21, < 2.20.24
Github	Github	>= 2.21.0, < 2.21.15
Github	Github	>= 2.22.0, < 2.22.7
Github	Github	>= 3.0.0, < 3.0.1

References

Timeline

Published: Mar 3, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-22861?

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.

How severe is CVE-2021-22861?

CVE-2021-22861 has a CVSS score of 6.5/10 (MEDIUM severity). The EPSS model estimates a 0.92% probability of exploitation in the next 30 days.

How do I fix CVE-2021-22861?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.