What’s Vulnerable › Vulnerabilities

CVE-2021-31553

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-04-22 · updated 2026-06-17
• Weakness: CWE-428

Description

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

• Wikimedia Foundation MediaWiki: through 1.35.2

References

• https://gerrit.wikimedia.org/r/c/mediawiki/extensions/CheckUser/+/666963
• https://gerrit.wikimedia.org/r/c/mediawiki/extensions/CheckUser/+/666964
• https://gerrit.wikimedia.org/r/c/mediawiki/extensions/CheckUser/+/667023
• https://gerrit.wikimedia.org/r/c/mediawiki/extensions/CheckUser/+/667024
• https://gerrit.wikimedia.org/r/c/mediawiki/extensions/CheckUser/+/667025
• https://gerrit.wikimedia.org/r/c/mediawiki/extensions/CheckUser/+/667027
• https://phabricator.wikimedia.org/T275669
• https://gerrit.wikimedia.org/r/c/mediawiki/extensions/CheckUser/+/666963
• https://gerrit.wikimedia.org/r/c/mediawiki/extensions/CheckUser/+/666964
• https://gerrit.wikimedia.org/r/c/mediawiki/extensions/CheckUser/+/667023
• https://gerrit.wikimedia.org/r/c/mediawiki/extensions/CheckUser/+/667024
• https://gerrit.wikimedia.org/r/c/mediawiki/extensions/CheckUser/+/667025

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