CVE-2021-22861 Explained : Impact and Mitigation

This article discusses the improper access control vulnerability identified in GitHub Enterprise Server, allowing authenticated users to gain unauthorized write access to certain repositories.

Understanding CVE-2021-22861

This section will cover what CVE-2021-22861 entails and its impact.

What is CVE-2021-22861?

CVE-2021-22861 is an improper access control vulnerability in GitHub Enterprise Server that enables authenticated users to write to unauthorized repositories through specific pull requests and REST API requests.

The Impact of CVE-2021-22861

The vulnerability permitted users to write to unauthorized repositories, bypassing default settings for private repositories. It affected GitHub Enterprise Server versions since 2.4.21.

Technical Details of CVE-2021-22861

This section will delve into the vulnerability description, affected systems, and exploitation mechanism.

Vulnerability Description

The flaw allowed users to gain write access by forking the targeted repository, with branch protections partially mitigating unauthorized commits.

Affected Systems and Versions

GitHub Enterprise Server versions 2.20 to 3.0 were affected, with specific versions like 2.20.24 and 3.0.1 being vulnerable.

Exploitation Mechanism

Attackers could exploit the vulnerability via crafted pull requests and REST API requests, gaining unauthorized write access.

Mitigation and Prevention

This section will guide on immediate steps and long-term security practices to prevent such vulnerabilities.

Immediate Steps to Take

Users should apply the provided patches (2.20.24, 2.21.15, 2.22.7, 3.0.1) and enforce branch protections for additional security.

Long-Term Security Practices

Regularly update GitHub Enterprise Server, review repository settings, and monitor for any unauthorized access attempts.

Patching and Updates

Ensure timely installation of security patches and updates to address known vulnerabilities and protect repositories.