CVE-2021-39881 Explained : Impact and Mitigation

This article provides details about CVE-2021-39881, a vulnerability in GitLab that allows a malicious user to create an OAuth client application with arbitrary scope names, potentially leading to unauthorized access.

Understanding CVE-2021-39881

CVE-2021-39881 is a security vulnerability in GitLab that affects various versions, allowing malicious users to exploit OAuth client application creation.

What is CVE-2021-39881?

In all versions of GitLab CE/EE since version 7.7, a vulnerability exists where a malicious user can create an OAuth client application with arbitrary scope names. This could deceive unsuspecting users into authorizing the malicious application using spoofed scope names and descriptions.

The Impact of CVE-2021-39881

The vulnerability has a CVSS base score of 3.5 (Low), affecting integrity and user interaction but not confidentiality or availability. The attack vector is network-based with low complexity.

Technical Details of CVE-2021-39881

This section delves into the specifics of the vulnerability in GitLab.

Vulnerability Description

The vulnerability involves insufficient verification of data authenticity in GitLab, enabling the creation of OAuth client applications with misleading scope names.

Affected Systems and Versions

Product: GitLab
Vendor: GitLab
Versions:
=7.7, <14.1.7

=14.2, <14.2.5

=14.3, <14.3.1

Exploitation Mechanism

The flaw allows a malicious user to craft OAuth client applications with deceptive scope names, tricking users into authorizing them.

Mitigation and Prevention

To safeguard systems against CVE-2021-39881, follow these mitigation practices:

Immediate Steps to Take

Update GitLab to a secure version that addresses the vulnerability.
Promptly revoke access for any suspicious OAuth client applications.

Long-Term Security Practices

Implement strict OAuth client application approval processes.
Educate users on recognizing and authorizing legitimate applications.

Patching and Updates

Regularly apply security patches and updates provided by GitLab to address known vulnerabilities.