CVE-2021-31553 : Security Advisory and Response

An issue was discovered in the CheckUser extension for MediaWiki through version 1.35.2, where MediaWiki usernames with trailing whitespace could be stored in the cu_log database table, leading to denial of service for certain CheckUser extension pages and functionality. Attackers could exploit this vulnerability to interfere with usage tracking by turning off Special:CheckUserLog.

Understanding CVE-2021-31553

This CVE details a security flaw in the CheckUser extension for MediaWiki, impacting versions up to 1.35.2.

What is CVE-2021-31553?

CVE-2021-31553 is a vulnerability in MediaWiki that allows malicious actors to store usernames with trailing whitespace in the database, resulting in denial of service for specific CheckUser extension pages and features.

The Impact of CVE-2021-31553

The exploitation of this vulnerability could disrupt usage tracking by manipulating the Special:CheckUserLog function, thereby affecting the functionality of the CheckUser extension in MediaWiki.

Technical Details of CVE-2021-31553

The technical aspects of CVE-2021-31553 include:

Vulnerability Description

The CheckUser extension for MediaWiki up to version 1.35.2 is susceptible to storing usernames with trailing whitespace, causing a denial of service for select CheckUser extension pages and operations.

Affected Systems and Versions

All versions of MediaWiki up to 1.35.2 utilizing the CheckUser extension are impacted by this vulnerability.

Exploitation Mechanism

By storing usernames with trailing whitespace in the cu_log database table, threat actors can disrupt CheckUser extension pages and interfere with usage tracking through manipulation of Special:CheckUserLog.

Mitigation and Prevention

To address CVE-2021-31553, consider the following actions:

Immediate Steps to Take

Upgrade MediaWiki to version 1.35.2 or later to mitigate the vulnerability.
Monitor system logs for any suspicious activity related to user data storage.

Long-Term Security Practices

Regularly update extensions and plugins to their latest versions to prevent security loopholes.
Conduct security audits and testing to identify and resolve vulnerabilities proactively.

Patching and Updates

Stay informed about security patches released by MediaWiki and promptly apply them to ensure protection against known vulnerabilities.