An issue was discovered in the CheckUser extension for MediaWiki before 1.35.12, 1.36.x through 1.39.x before 1.39.5, and 1.40.x before 1.4…

published 2023-10-09 3 y ago modified 2026-06-17 4 mo ago also BIT-mediawiki-2023-45367 , EUVD-2023-49659

cvss: 6.5; 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 51%
public exploits: 0; none known

An issue was discovered in the CheckUser extension for MediaWiki before 1.35.12, 1.36.x through 1.39.x before 1.39.5, and 1.40.x before 1.40.1. A user can use a rest.php/checkuser/v0/useragent-clienthints/revision/ URL to store an arbitrary number of rows in cu_useragent_clienthints, leading to a denial of service.

Patch / fix

fixed in 2

bitnami mediawiki 1.35.12, 1.39.5, 1.40.1
mediawiki mediawiki 1.35.12, 1.39.5

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: partial
Assessed: 2 y ago (2024-09-19)

Exploit prediction

0.66% chance of exploitation in the next 30 days, higher than 51% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

phabricator.wikimedia.org https://phabricator.wikimedia.org/T344923 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
NVD	3.1	6.5	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
OSV	3.1	6.5	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem	package	affected	fixed in
bitnami	mediawiki	<1.35.12 >=1.36.0, <1.39.5 >=1.40.0, <1.40.1	1.35.12 1.39.5 1.40.1

References

phabricator.wikimedia.org /T344923
exploit, issue-tracking, vendor-advisory, web
nvd.nist.gov /vuln/detail/CVE-2023-45367
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