What is CVE-2021-45472?

CVE-2021-45472 is a medium-severity vulnerability in MediaWiki, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2021-12-24.

How severe is CVE-2021-45472?

Medium severity. CVSS v3 base score is 6.1 out of 10.

XSS in MediaWiki

CVE-2021-45472

In MediaWiki through 1.37, XSS can occur in Wikibase because an external identifier property can have a URL format that includes a $1 formatter substitution marker, and the javascript: URL scheme (among others) can be used.

Vulnerability class: XSS (Cross-Site Scripting)

Published 2021-12-24 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.010 (60.7th percentile), scored 2026-10-02.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 61st percentile — 60.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.010 · newest: 0.010 · change: 0.000

Affected products

MediaWiki
Fedoraproject Fedora — versions 35

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

phabricator.wikimedia.org/T297570 (Third Party Advisory)
gerrit.wikimedia.org/r/q/I37ece1dfdc80d38055067c9c4fa73ba591acd8bd (Third Party Advisory)
lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/… (vendor-advisory)

Frequently asked questions

What is CVE-2021-45472?: CVE-2021-45472 is a medium-severity vulnerability in MediaWiki, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2021-12-24.
How severe is CVE-2021-45472?: Medium severity. CVSS v3 base score is 6.1 out of 10.