CVE-2026-81918: Concretecms Concrete CMS

Medium severity, CVSS 4.8. EPSS: 0.3% chance of exploitation in the next 30 days.

Concrete CMS below 9.5.3 is vulnerable to Stored XSS via the Date Format field in the Page Attribute Display block. A user with edit_page_contents permissions could store a payload which executes in the browser of any visitor who viewed a page where the block was configured to display a date-type attribute. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 4.8 with vector CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N. Thanks Oriol Ortiz for reporting.

Affected products

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

Published 2026-09-11. Last modified 2026-09-18.