CVE-2021-21670 : What You Need to Know

Jenkins 2.299 and earlier, LTS 2.289.1 and earlier versions have a vulnerability that allows users to cancel queue items and abort builds without the necessary permissions.

Understanding CVE-2021-21670

This CVE affects Jenkins, specifically versions 2.299 and below, including LTS 2.289.1 and previous releases.

What is CVE-2021-21670?

The vulnerability in Jenkins allows users with Item/Cancel permission to cancel queue items and abort builds, even if they do not possess Item/Read permission.

The Impact of CVE-2021-21670

Attackers could exploit this vulnerability to disrupt the build process and potentially cause denial of service by unauthorized cancellation of jobs.

Technical Details of CVE-2021-21670

The technical details of this CVE include:

Vulnerability Description

The vulnerability arises from incorrect authorization handling, specifically allowing users to cancel jobs without the necessary read permissions.

Affected Systems and Versions

Jenkins versions 2.299 and below, as well as LTS 2.289.1 and earlier, are impacted by this vulnerability.

Exploitation Mechanism

Attackers can exploit this vulnerability by leveraging the cancel queue items and abort builds functionality without the required permissions.

Mitigation and Prevention

To mitigate the risks associated with CVE-2021-21670, consider the following steps:

Immediate Steps to Take

Upgrade Jenkins to a fixed version that addresses the authorization issue.
Restrict access to sensitive Jenkins functionalities based on the principle of least privilege.

Long-Term Security Practices

Regularly review and update access control policies within Jenkins.
Educate users on proper job management practices to prevent unauthorized actions.

Patching and Updates

Stay informed about security advisories and promptly apply patches released by Jenkins to address known vulnerabilities.