CVE-2026-18422: Concretecms Concrete CMS

Medium severity, CVSS 6.5. EPSS: 0.4% chance of exploitation in the next 30 days.

Concrete CMS before 9.5.3 did not enforce a destination-side authorization check and did not validate a CSRF token in the multilingual page assignment backend action (Backend\Page\Multilingual::assign). As a result, an authenticated user who held the Edit Page Multilingual Settings permission on a single page could bind an arbitrary page in another locale as that source page's translation, and could delete legitimate translation pairs maintained by other editors, altering public-facing language routing across the site. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 2.1 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N. Thanks Winston Crooker for reporting.

Affected products

• Concretecms Concrete CMS: before 9.5.3 (fixed in 9.5.3)

Published 2026-09-15. Last modified 2026-09-21.