CVE-2021-29453 : Security Advisory and Response

A denial-of-service vulnerability, tracked as CVE-2021-29453, exists in the matrix-media-repo open-source media repository for Matrix. The vulnerability allows a malicious user to exhaust server memory by uploading small images that expand to have large dimensions during thumbnail processing, leading to denial of service.

Understanding CVE-2021-29453

This section will cover what CVE-2021-29453 is, its impact, technical details, and mitigation strategies.

What is CVE-2021-29453?

CVE-2021-29453 is a denial-of-service vulnerability in matrix-media-repo versions 1.2.6 and earlier. Malicious users can exploit the vulnerability by uploading small images that expand to consume excessive server memory during thumbnail generation.

The Impact of CVE-2021-29453

The vulnerability has a CVSS base score of 5.7, indicating a medium severity issue. It poses a high availability impact, requiring low privileges and user interaction, with a network-based attack vector.

Technical Details of CVE-2021-29453

This section will delve into the vulnerability description, affected systems, affected versions, and the exploitation mechanism.

Vulnerability Description

matrix-media-repo versions 1.2.6 and earlier do not handle malicious images properly, resulting in memory exhaustion during thumbnail creation, leading to a denial-of-service condition.

Affected Systems and Versions

The vulnerability affects matrix-media-repo versions <= 1.2.6.

Exploitation Mechanism

Malicious users can upload small images that become memory-intensive during thumbnail processing, causing the server to exhaust memory resources, resulting in denial of service.

Mitigation and Prevention

This section outlines immediate steps to take and long-term security practices to mitigate the CVE-2021-29453 vulnerability.

Immediate Steps to Take

Users should update to version 1.2.7 of matrix-media-repo, which contains a fix for the vulnerability. It is crucial to apply patches promptly to prevent exploitation.

Long-Term Security Practices

Implement strict image processing controls, monitor server memory usage, and regularly update matrix-media-repo to protect against potential denial-of-service attacks.

Patching and Updates

Regularly check for security advisories, apply vendor patches promptly, and maintain up-to-date software versions to address known vulnerabilities and enhance system security.