CVE-2021-39939 : Exploit Details and Defense Strategies

GitLab Runner versions >=13.7, <14.3.6, >=14.4, <14.4.4, and >=14.5, <14.5.2 are affected by an uncontrolled resource consumption vulnerability.

Understanding CVE-2021-39939

This CVE involves an uncontrolled resource consumption vulnerability in GitLab Runner.

What is CVE-2021-39939?

The vulnerability affects GitLab Runner versions between 13.7 to 14.5.2
It allows an attacker to exhaust resources on the runner manager by triggering a job with a specially crafted docker image.

The Impact of CVE-2021-39939

CVSS Score: 6.5 (Medium)
Attack Vector: Network
Availability Impact: High
The vulnerability was discovered internally by the GitLab team.

Technical Details of CVE-2021-39939

The technical details of the CVE provide insight into the vulnerability and affected systems.

Vulnerability Description

An uncontrolled resource consumption issue in GitLab Runner

Affected Systems and Versions

GitLab Runner versions >=13.7, <14.3.6
GitLab Runner versions >=14.4, <14.4.4
GitLab Runner versions >=14.5, <14.5.2

Exploitation Mechanism

Attacker triggers a job with a malicious docker image to deplete resources on the runner manager

Mitigation and Prevention

Taking immediate steps and implementing long-term security practices are crucial to safeguard systems.

Immediate Steps to Take

Update GitLab Runner to versions 14.3.6, 14.4.4, or 14.5.2
Monitor resource usage and restrict access to vulnerable systems

Long-Term Security Practices

Regular security audits and penetration testing
Employee training on identifying suspicious job triggers

Patching and Updates

Apply the latest patches and updates released by GitLab to fix the vulnerability