CVE-2021-31553

Name: CVE-2021-31553
Creator: NVD / NIST
Published: 2021-04-22T03:15:08.197+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 6.5/10EPSS 1.40%

Last modified Jun 17, 2026

CVE-2021-31553 is a medium-severity vulnerability rated 6.5/10 on the CVSS scale. 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. EPSS estimates a 1.40% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

6.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L

EPSS Probability

1.40%

69.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-428

Affected Software

Vendor	Product	Versions
Mediawiki	Mediawiki	<= 1.35.2

References

https://gerrit.wikimedia.org/r/c/mediawiki/extensions/CheckUser/+/666963Issue Tracking, Third Party Advisory
https://gerrit.wikimedia.org/r/c/mediawiki/extensions/CheckUser/+/666964Issue Tracking, Third Party Advisory
https://gerrit.wikimedia.org/r/c/mediawiki/extensions/CheckUser/+/667023Issue Tracking, Third Party Advisory
https://gerrit.wikimedia.org/r/c/mediawiki/extensions/CheckUser/+/667024Issue Tracking, Third Party Advisory
https://gerrit.wikimedia.org/r/c/mediawiki/extensions/CheckUser/+/667025Issue Tracking, Third Party Advisory
https://gerrit.wikimedia.org/r/c/mediawiki/extensions/CheckUser/+/667027Issue Tracking, Third Party Advisory
https://phabricator.wikimedia.org/T275669Third Party Advisory
https://gerrit.wikimedia.org/r/c/mediawiki/extensions/CheckUser/+/666963Issue Tracking, Third Party Advisory
https://gerrit.wikimedia.org/r/c/mediawiki/extensions/CheckUser/+/666964Issue Tracking, Third Party Advisory
https://gerrit.wikimedia.org/r/c/mediawiki/extensions/CheckUser/+/667023Issue Tracking, Third Party Advisory
https://gerrit.wikimedia.org/r/c/mediawiki/extensions/CheckUser/+/667024Issue Tracking, Third Party Advisory
https://gerrit.wikimedia.org/r/c/mediawiki/extensions/CheckUser/+/667025Issue Tracking, Third Party Advisory
https://gerrit.wikimedia.org/r/c/mediawiki/extensions/CheckUser/+/667027Issue Tracking, Third Party Advisory
https://phabricator.wikimedia.org/T275669Third Party Advisory

Timeline

Published: Apr 22, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-31553?

How severe is CVE-2021-31553?

CVE-2021-31553 has a CVSS score of 6.5/10 (MEDIUM severity). The EPSS model estimates a 1.40% probability of exploitation in the next 30 days.

How do I fix CVE-2021-31553?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-31553?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST