CVE-2021-39947 : Vulnerability Insights and Analysis

This CVE-2021-39947 article provides insights into a vulnerability detected in GitLab Runner versions up to 14.3.4, 14.4 to 14.4.2, and 14.5 to 14.5.2, emphasizing the potential risks and mitigation strategies.

Understanding CVE-2021-39947

CVE-2021-39947 pertains to a significant vulnerability in GitLab Runner, impacting various versions and potentially exposing sensitive information.

What is CVE-2021-39947?

In specific scenarios, GitLab Runner versions mentioned above could reuse file descriptor 0 for multiple traces, resulting in mixed outputs from different jobs.

The Impact of CVE-2021-39947

This vulnerability has a CVSSv3.1 base score of 5.3 (Medium severity), with confidentiality impact rated as High.

Technical Details of CVE-2021-39947

This section delves into the technical specifics of the CVE, including the vulnerability description, affected systems, and exploitation method.

Vulnerability Description

The issue arises in how trace file buffers in affected GitLab Runner versions handle file descriptors, leading to output mix-up between multiple jobs.

Affected Systems and Versions

Product: GitLab Runner
Vendor: GitLab
Versions:
<14.3.4

=14.4, <14.4.2

=14.5, <14.5.2

Exploitation Mechanism

The vulnerability can be exploited by manipulating trace file buffers to mix outputs, potentially exposing sensitive data to unauthorized entities.

Mitigation and Prevention

Explore the necessary steps to secure systems and prevent exploitation of this vulnerability.

Immediate Steps to Take

Upgrade GitLab Runner to version 14.5.2 or later to mitigate the vulnerability.
Monitor system logs for any unusual activity related to file descriptor usage.

Long-Term Security Practices

Regularly update and patch GitLab Runner to ensure the latest security fixes are in place.
Implement access controls and monitoring mechanisms to prevent unauthorized access to file descriptors.

Patching and Updates

GitLab has released patches addressing this vulnerability. Ensure timely application of these patches to safeguard systems.