CVE-2021-31553: Mediawiki

Medium severity, CVSS 6.5. EPSS: 1.4% chance of exploitation in the next 30 days.

An issue was discovered in the CheckUser extension for MediaWiki through 1.35.2. MediaWiki usernames with trailing whitespace could be stored in the cu_log database table such that denial of service occurred for certain CheckUser extension pages and functionality. For example, the attacker could turn off Special:CheckUserLog and thus interfere with usage tracking.

Affected products

• Mediawiki Mediawiki: up to and including 1.35.2

Published 2021-04-22. Last modified 2026-06-17.