CVE-2021-21610 : What You Need to Know

This article provides detailed information about CVE-2021-21610, a vulnerability found in Jenkins versions 2.274 and earlier, LTS 2.263.1 and earlier that exposes users to cross-site scripting attacks.

Understanding CVE-2021-21610

CVE-2021-21610 is a security vulnerability in Jenkins that arises from inadequate restrictions on URL rendering, allowing for cross-site scripting (XSS) attacks if unsafe elements are not prohibited by the configured markup formatter.

What is CVE-2021-21610?

Jenkins versions 2.274 and earlier, LTS 2.263.1 and earlier are susceptible to reflected cross-site scripting (XSS) attacks due to the lack of restrictions on URL rendering of formatted markup passed as a query parameter.

The Impact of CVE-2021-21610

This vulnerability could be exploited by attackers to execute malicious scripts in the context of the web browser of a user who clicks on a crafted link, potentially leading to unauthorized actions or data theft.

Technical Details of CVE-2021-21610

CVE ID: CVE-2021-21610 Published Date: January 13, 2021 Updated Date: October 24, 2023 Affected Versions: Jenkins 2.274 and earlier, LTS 2.263.1 and earlier

Vulnerability Description

Jenkins' failure to enforce restrictions on URL rendering for formatted markup allows for the injection of malicious scripts leading to cross-site scripting (XSS) attacks.

Affected Systems and Versions

Jenkins versions 2.274 and earlier
LTS versions 2.263.1 and earlier

Exploitation Mechanism

Attackers can craft URLs with malicious scripts passed as query parameters, exploiting the vulnerability to execute unauthorized scripts in users' browsers.

Mitigation and Prevention

To address CVE-2021-21610, immediate action and long-term security practices are essential.

Immediate Steps to Take

Update Jenkins to the latest version to mitigate the vulnerability
Configure Jenkins to restrict unsafe elements in markup for added security

Long-Term Security Practices

Regularly monitor Jenkins security advisories for updates
Educate users about safe browsing practices to prevent XSS attacks

Patching and Updates

Stay informed about security patches and promptly apply them to Jenkins to safeguard against known vulnerabilities.