An issue was discovered in MediaWiki before 1.35.5, 1.36.x before 1.36.3, and 1.37.x before 1.37.1.

published 2022-01-07 4 y ago modified 2026-06-17 4 mo ago also BIT-mediawiki-2021-46150 , EUVD-2021-32850

cvss: 4.8; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 0.7%; EPSS 0.7% chance of exploitation in 30 days, percentile 52%
public exploits: 0; none known

An issue was discovered in MediaWiki before 1.35.5, 1.36.x before 1.36.3, and 1.37.x before 1.37.1. Special:CheckUserLog allows CheckUser XSS because of date mishandling, as demonstrated by an XSS payload in MediaWiki:October.

Patch / fix

fixed in 2 links 1

bitnami mediawiki 1.35.5, 1.36.3, 1.37.1
mediawiki mediawiki 1.35.5, 1.36.3, 1.37.1

gerrit.wikimedia.org/r/plugins/gitiles/mediawiki/extensions/CheckUser/+/79c2c49… commit

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-46150 updated 2025-11-21 cvss 4.8

mediawiki: XSS because of date mishandling

Red Hat OpenShift Container Platform 3.11 mediawiki
not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.67% chance of exploitation in the next 30 days, higher than 52% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

phabricator.wikimedia.org https://phabricator.wikimedia.org/T292795 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
NVD	3.1	4.8	CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N
NVD	2.0	3.5	AV:N/AC:M/Au:S/C:N/I:P/A:N
OSV	3.1	4.8	CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N

Affected packages

ecosystem	package	affected	fixed in
bitnami	mediawiki	<1.35.5 >=1.36.0, <1.36.3 >=1.37.0, <1.37.1	1.35.5 1.36.3 1.37.1

Classification

Weakness

CWE-79 Improper Neutralization of Input During Web Page Generation

References

gerrit.wikimedia.org /r/plugins/gitiles/mediawiki/extensions/CheckUser/+/79c2c49a18f96b159258958feca90fce964c350a
third-party-advisory, web
phabricator.wikimedia.org /T292795
exploit, third-party-advisory, web
nvd.nist.gov /vuln/detail/CVE-2021-46150
web

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary