What is CVE-2021-31548?

CVE-2021-31548 is a medium-severity vulnerability in MediaWiki, classified under Incorrect Authorization. CVSS score: 6.5/10. Published 2021-04-22.

How severe is CVE-2021-31548?

Medium severity. CVSS v3 base score is 6.5 out of 10.

Auth bypass in MediaWiki

CVE-2021-31548

An issue was discovered in the AbuseFilter extension for MediaWiki through 1.35.2. A MediaWiki user who is partially blocked or was unsuccessfully blocked could bypass AbuseFilter and have their edits completed.

Vulnerability class: Broken Access Control

Published 2021-04-22 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N.

EPSS exploit prediction

EPSS: 0.007 (51.1th percentile), scored 2026-10-01.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 51st percentile — 51.1% 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-863 — Incorrect Authorization

References

phabricator.wikimedia.org/T272333 (Third Party Advisory)
gerrit.wikimedia.org/r/q/Ifac795125927d584a31d95e1b4c4241eef860fa1 (Third Party Advisory, Issue Tracking)

Frequently asked questions

What is CVE-2021-31548?: CVE-2021-31548 is a medium-severity vulnerability in MediaWiki, classified under Incorrect Authorization. CVSS score: 6.5/10. Published 2021-04-22.
How severe is CVE-2021-31548?: Medium severity. CVSS v3 base score is 6.5 out of 10.