CVE-2021-36126

Name: CVE-2021-36126
Creator: NVD / NIST
Published: 2021-07-02T13:15:07.787+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.8/10EPSS 1.20%

Last modified Jun 17, 2026

CVE-2021-36126 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. An issue was discovered in the AbuseFilter extension in MediaWiki through 1.36. If the MediaWiki:Abusefilter-blocker message is invalid within the content language, the filter user falls back to the English version, but that English version could also be invalid on a wiki. EPSS estimates a 1.20% chance of exploitation in the next 30 days.

Description

An issue was discovered in the AbuseFilter extension in MediaWiki through 1.36. If the MediaWiki:Abusefilter-blocker message is invalid within the content language, the filter user falls back to the English version, but that English version could also be invalid on a wiki. This would result in a fatal error, and potentially fail to block or restrict a potentially nefarious user.

Metrics

CVSS 3.1

9.8/10

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

EPSS Probability

1.20%

64.3th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Vendor	Product	Versions
Mediawiki	Mediawiki	<= 1.36

References

https://gerrit.wikimedia.org/r/q/I9e9f44b7663e810de70fb9ac7f6760f83dd4895bPatch, Vendor Advisory
https://phabricator.wikimedia.org/T284364Exploit, Issue Tracking, Patch, Vendor Advisory
https://gerrit.wikimedia.org/r/q/I9e9f44b7663e810de70fb9ac7f6760f83dd4895bPatch, Vendor Advisory
https://phabricator.wikimedia.org/T284364Exploit, Issue Tracking, Patch, Vendor Advisory

Timeline

Published: Jul 2, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-36126?

How severe is CVE-2021-36126?

CVE-2021-36126 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 1.20% probability of exploitation in the next 30 days.

How do I fix CVE-2021-36126?

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-2021-36126?

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

Scan your code now

Source: NVD / NIST