Mediawiki · Mediawiki Checkuser Extension · CVE-2023-45367
**Name of the Vulnerable Software and Affected Versions**
MediaWiki CheckUser extension versions 1.35.12 and earlier, versions 1.36.x through 1.39.x before 1.39.5, and versions 1.40.x before 1.40.1
**Description**
An issue was discovered in the CheckUser extension for MediaWiki. 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. The exploitation of this issue may allow a remote attacker to cause a denial of service.
**Recommendations**
For MediaWiki CheckUser extension versions 1.35.12 and earlier, update to version 1.35.12 or later.
For MediaWiki CheckUser extension versions 1.36.x through 1.39.x before 1.39.5, update to version 1.39.5 or later.
For MediaWiki CheckUser extension versions 1.40.x before 1.40.1, update to version 1.40.1 or later.
As a temporary workaround, consider restricting access to the "rest.php/checkuser/v0/useragent-clienthints/revision/" URL to minimize the risk of exploitation.