CVE-2021-39871 Explained : Impact and Mitigation

This CVE article provides insights into a security vulnerability in GitLab affecting versions 13.0 to 14.3.1.

Understanding CVE-2021-39871

CVE-2021-39871 is a vulnerability in GitLab that allows attackers to bypass certain settings using a crafted API call.

What is CVE-2021-39871?

In all versions of GitLab since 13.0, a security flaw enables an attacker to bypass the setting that disables Bitbucket Server import with a specially created API call.

The Impact of CVE-2021-39871

The vulnerability has a base score of 4.3 (Medium severity) with low integrity impact and requires low privileges. It can be exploited over the network without user interaction.

Technical Details of CVE-2021-39871

This section delves into the technical aspects of the vulnerability.

Vulnerability Description

The vulnerability involves improper authorization in GitLab, enabling an attacker to bypass the Bitbucket Server import disable setting.

Affected Systems and Versions

Affected Product: GitLab
Affected Versions: >=13.0, <14.1.7, >=14.2, <14.2.5, >=14.3, <14.3.1

Exploitation Mechanism

Attackers can exploit this vulnerability by making a crafted API call to bypass security settings.

Mitigation and Prevention

Here are ways to address and prevent the CVE-2021-39871 vulnerability.

Immediate Steps to Take

Update affected GitLab instances to versions 14.1.7, 14.2.5, or 14.3.1 to mitigate the issue.
Monitor for any unusual API calls or activities.

Long-Term Security Practices

Regularly review and update security settings in GitLab.
Conduct security trainings to educate users on identifying and reporting suspicious activities.

Patching and Updates

GitLab has released patches in versions 14.1.7, 14.2.5, and 14.3.1 to address this vulnerability.