CVE-2021-21685 : What You Need to Know

Jenkins 2.318 and earlier, LTS 2.303.2 and earlier versions have a vulnerability where agent-to-controller access is not properly checked when creating parent directories in FilePath#mkdirs.

Understanding CVE-2021-21685

This CVE affects Jenkins, specifically versions 2.318 and below, as well as LTS 2.303.2 and earlier. The issue arises from a lack of proper verification of agent-to-controller access during directory creation in FilePath#mkdirs.

What is CVE-2021-21685?

The vulnerability identified as CVE-2021-21685 in Jenkins allows unauthorized agents to create directories without proper access verification, potentially leading to security breaches.

The Impact of CVE-2021-21685

The lack of validation for agent-to-controller access in Jenkins versions mentioned could be exploited by malicious agents to create directories without proper authorization, posing a security risk to the system.

Technical Details of CVE-2021-21685

This section outlines the specifics of the vulnerability.

Vulnerability Description

Jenkins 2.318 and earlier, LTS 2.303.2 and earlier versions fail to validate agent-to-controller access when creating parent directories using FilePath#mkdirs, which could be exploited by unauthorized agents.

Affected Systems and Versions

The vulnerability affects Jenkins versions up to 2.318 and LTS versions up to 2.303.2.

Exploitation Mechanism

Unauthorized agents can exploit this flaw by bypassing the directory creation access checks, potentially leading to unauthorized directory creation.

Mitigation and Prevention

Here are the necessary steps to address and prevent exploitation of CVE-2021-21685.

Immediate Steps to Take

It is advised to update Jenkins to a fixed version that addresses this vulnerability. Ensure proper access controls and monitoring are in place.

Long-Term Security Practices

Regularly update Jenkins to the latest versions, maintain proper access control configurations, and educate users on secure coding practices to mitigate similar vulnerabilities.

Patching and Updates

Stay informed about security advisories and patch releases from Jenkins. Promptly apply patches and updates to protect the system from known vulnerabilities.