CVE-2021-22869 : Exploit Details and Defense Strategies

An improper access control vulnerability in GitHub Enterprise Server allowed a workflow job to execute in a self-hosted runner group it should not have had access to. This affects customers using self-hosted runner groups for access control. Read on to understand the impact, technical details, and mitigation steps related to CVE-2021-22869.

Understanding CVE-2021-22869

GitHub Enterprise Server versions 3.0.0 to 3.0.15 and 3.1.0 to 3.1.7 were affected by an improper access control vulnerability, allowing code execution by an incorrect runner group within the organization.

What is CVE-2021-22869?

CVE-2021-22869 is an improper access control vulnerability in GitHub Enterprise Server that could lead to unintended code execution by a self-hosted runner group not authorized to do so.

The Impact of CVE-2021-22869

This vulnerability allowed repositories with access to one enterprise runner group to execute code in all enterprise runner groups within the organization, leading to potential security risks and code execution by unauthorized runner groups.

Technical Details of CVE-2021-22869

The following technical details provide insight into the vulnerability:

Vulnerability Description

The vulnerability in GitHub Enterprise Server allowed workflow jobs to execute in runner groups they shouldn't have had access to, potentially causing code to be run unintentionally.

Affected Systems and Versions

GitHub Enterprise Server versions 3.0.0 to 3.0.15 and 3.1.0 to 3.1.7 were impacted, while versions 3.0.16 and 3.1.8 contained fixes for this vulnerability.

Exploitation Mechanism

Improper authentication checks during requests allowed repositories to access unauthorized runner groups, leading to code execution by incorrect runner groups.

Mitigation and Prevention

To address the CVE-2021-22869 vulnerability, consider the following mitigation strategies:

Immediate Steps to Take

Immediately update GitHub Enterprise Server to versions 3.0.16 or 3.1.8 to mitigate the vulnerability and prevent unauthorized code execution.

Long-Term Security Practices

Regularly review and update access controls for self-hosted runner groups to ensure only authorized entities can execute workflow jobs.

Patching and Updates

Stay informed about security updates and patches released by GitHub to address vulnerabilities like CVE-2021-22869 and apply them promptly to enhance system security.