CVE-2021-21684 : Exploit Details and Defense Strategies

Jenkins Git Plugin version 4.8.2 and earlier are vulnerable to a stored cross-site scripting (XSS) attack due to improper handling of Git SHA-1 checksum parameters. This CVE was published on October 6, 2021, by Jenkins.

Understanding CVE-2021-21684

This section provides insights into the nature of the vulnerability and its impact.

What is CVE-2021-21684?

CVE-2021-21684 specifically affects Jenkins Git Plugin versions 4.8.2 and earlier, allowing attackers to exploit a stored cross-site scripting vulnerability through unescaped Git SHA-1 checksum parameters in commit notifications.

The Impact of CVE-2021-21684

The vulnerability can be exploited by malicious actors to execute arbitrary code within the context of the application, potentially leading to sensitive data exposure, unauthorized actions, and compromise of the Jenkins environment.

Technical Details of CVE-2021-21684

This section delves into the technical aspects of the CVE, including affected systems and exploitation mechanisms.

Vulnerability Description

Jenkins Git Plugin versions 4.8.2 and below fail to properly escape Git SHA-1 checksum parameters in commit notifications, enabling attackers to inject malicious scripts and launch cross-site scripting attacks.

Affected Systems and Versions

All versions of Jenkins Git Plugin up to and including 4.8.2 are impacted by this vulnerability, whereas versions 4.7.1.1 and 4.3.1 are unaffected.

Exploitation Mechanism

Attackers can exploit this vulnerability by manipulating Git SHA-1 checksum parameters in commit notifications to inject and execute malicious scripts, potentially leading to the compromise of user data and system integrity.

Mitigation and Prevention

In this section, we explore the steps to mitigate the risks posed by CVE-2021-21684 and prevent future vulnerabilities.

Immediate Steps to Take

Users are advised to upgrade Jenkins Git Plugin to version 4.8.3 or higher to mitigate the XSS vulnerability. Additionally, ensure that input data is properly sanitized and validate user inputs to prevent script injection attacks.

Long-Term Security Practices

Implement secure coding practices, conduct regular security audits, and stay informed about security patches and updates for Jenkins and associated plugins to maintain a robust defense against XSS and other security threats.

Patching and Updates

Stay updated with security advisories from Jenkins and promptly apply patches and updates to all Jenkins components and plugins to address known vulnerabilities and enhance the overall security posture of your Jenkins environment.