CVE-2021-42040 : What You Need to Know

An issue was discovered in MediaWiki through 1.36.2 where a parser function related to loop control allowed for an infinite loop within the Loops extension, potentially leading to memory exhaustion.

Understanding CVE-2021-42040

What is CVE-2021-42040?

This CVE identifies a vulnerability in MediaWiki that could result in an infinite loop and memory exhaustion due to mishandling of the egLoopsCountLimit parser function related to loop control.

The Impact of CVE-2021-42040

The vulnerability could lead to memory exhaustion and a php-fpm hang within the Loops extension in MediaWiki version 1.36.2.

Technical Details of CVE-2021-42040

Vulnerability Description

The issue arises from mishandling the egLoopsCountLimit parser function, allowing for an infinite loop, potentially causing memory exhaustion.

Affected Systems and Versions

Affected software: MediaWiki through version 1.36.2

Exploitation Mechanism

The vulnerability can be exploited by triggering the parser function related to loop control, causing the Loops extension to enter an infinite loop.

Mitigation and Prevention

Immediate Steps to Take

Apply the latest patch or upgrade to a non-vulnerable version of MediaWiki.
Monitor system resources for signs of unusual memory consumption.

Long-Term Security Practices

Regularly update software to ensure patches for known vulnerabilities are applied promptly.
Conduct security audits and code reviews to detect and address similar issues.

Patching and Updates

Ensure you stay informed about security updates for MediaWiki and promptly apply patches to mitigate the risk of exploitation.