CVE-2021-39896 Explained : Impact and Mitigation

This CVE-2021-39896 informational article provides details about a vulnerability in GitLab that could lead to repudiation issues.

Understanding CVE-2021-39896

CVE-2021-39896 is a vulnerability in GitLab that allows an admin to be logged in as a different user after using the impersonate feature multiple times.

What is CVE-2021-39896?

In all versions of GitLab CE/EE since version 8.0, there exists a vulnerability where if an admin uses the impersonate feature twice and then stops impersonating, they may be logged in as the second user they impersonated. This issue could lead to repudiation problems.

The Impact of CVE-2021-39896

The impact of this vulnerability is rated as low. The base CVSS score is 3.8, indicating low severity with no availability impact and low impacts on confidentiality and integrity. The exploit requires high privileges but no user interaction.

Technical Details of CVE-2021-39896

This section provides technical details of the CVE-2021-39896 vulnerability in GitLab.

Vulnerability Description

The vulnerability involves improper access control in GitLab, allowing admins to be logged in as a different user.

Affected Systems and Versions

Affected versions include GitLab >=8.0, <14.1.7
Also affected are versions >=14.2, <14.2.5
Additionally, versions >=14.3, <14.3.1 are impacted

Exploitation Mechanism

The vulnerability can be exploited when an admin uses the impersonate feature twice and then stops impersonating, resulting in potential repudiation issues.

Mitigation and Prevention

To mitigate and prevent CVE-2021-39896, consider the following steps:

Immediate Steps to Take

Upgrade GitLab to a patched version
Monitor admin activities closely

Long-Term Security Practices

Implement proper access control measures
Educate admins on the risks of impersonation feature overuse

Patching and Updates

GitLab has released patches for the affected versions
Regularly update GitLab to the latest secure version