What is CVE-2021-42048?

CVE-2021-42048 is a medium-severity vulnerability in MediaWiki, classified under Cross-site Scripting. CVSS score: 4.8/10. Published 2022-09-29.

How severe is CVE-2021-42048?

Medium severity. CVSS v3 base score is 4.8 out of 10.

XSS in MediaWiki

CVE-2021-42048

An issue was discovered in the Growth extension in MediaWiki through 1.36.2. Any admin can add arbitrary JavaScript code to the Newcomer home page footer, which can be executed by viewers with zero edits.

Vulnerability class: XSS (Cross-Site Scripting)

Published 2022-09-29 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 4.8 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.007 (49.5th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 50th percentile — 49.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.007 · newest: 0.007 · change: 0.000

Affected products

MediaWiki

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

phabricator.wikimedia.org/T289064 (Patch, Vendor Advisory)
gerrit.wikimedia.org/r/q/Iaa90a8976834d70caad592e9d1b18510318db537 (Patch, Vendor Advisory)

Frequently asked questions

What is CVE-2021-42048?: CVE-2021-42048 is a medium-severity vulnerability in MediaWiki, classified under Cross-site Scripting. CVSS score: 4.8/10. Published 2022-09-29.
How severe is CVE-2021-42048?: Medium severity. CVSS v3 base score is 4.8 out of 10.