CVE-2021-29460 : What You Need to Know

A critical Cross-site scripting (XSS) vulnerability in Kirby CMS allows attackers to upload SVG files containing malicious scripts, potentially leading to privilege escalation and unauthorized access. The vulnerability affects Kirby versions prior to 3.5.4 and has a base severity score of 7.6.

Understanding CVE-2021-29460

This CVE describes a security issue in Kirby CMS that enables attackers to execute malicious scripts through unsanitized SVG file uploads, posing a significant risk to affected systems.

What is CVE-2021-29460?

Kirby CMS, versions below 3.5.4, are susceptible to Cross-site scripting (XSS) attacks through the upload of SVG files containing harmful scripts. Attackers can exploit this vulnerability to perform various actions with the victim's privileges, posing a serious security threat.

The Impact of CVE-2021-29460

The vulnerability allows attackers to execute arbitrary scripts by uploading SVG files with malicious content, potentially leading to unauthorized access, data theft, and privilege escalation. It poses a high risk, especially in environments with potential attackers within authenticated Panel users.

Technical Details of CVE-2021-29460

This section provides technical insights into the vulnerability, including its description, affected systems and versions, as well as the exploitation mechanism.

Vulnerability Description

A flaw in Kirby CMS allows malicious users to upload SVG files containing harmful scripts, enabling them to perform unauthorized actions on the victim's behalf. This security loophole can lead to severe consequences if exploited.

Affected Systems and Versions

The vulnerability impacts Kirby versions prior to 3.5.4, exposing systems that allow SVG file uploads in frontend forms without proper sanitization measures. Users of affected versions are advised to update to version 3.5.4 or newer to mitigate the risk.

Exploitation Mechanism

Attackers can leverage the vulnerability by uploading SVG files with malicious content, tricking authenticated users into executing harmful scripts. This exploitation method can result in unauthorized API requests and privilege escalation.

Mitigation and Prevention

To address CVE-2021-29460, immediate steps should be taken to secure vulnerable systems and prevent potential exploitation. Here are some key strategies:

Immediate Steps to Take

Update Kirby to version 3.5.4 or above to patch the vulnerability and protect systems from XSS attacks.
Disable the upload of SVG files in file blueprints as a temporary workaround until the update is applied.

Long-Term Security Practices

Regularly monitor for security advisories and updates from Kirby to stay informed about emerging threats and patches.
Implement strict file upload policies and sanitize all uploaded content to prevent malicious code execution.

Patching and Updates

Ensure that all frontend upload forms are patched to prevent the upload of SVG files with harmful scripts.
Follow best practices for secure coding and configuration to enhance the overall security posture of the system.