CVE-2021-40108: Concretecms Concrete CMS

High severity, CVSS 8.8. EPSS: 0.5% chance of exploitation in the next 30 days.

An issue was discovered in Concrete CMS through 8.5.5. The Calendar is vulnerable to CSRF. ccm_token is not verified on the ccm/calendar/dialogs/event/add/save endpoint.

Affected products

• Concretecms Concrete CMS: before 8.5.6 (fixed in 8.5.6)

Published 2021-09-27. Last modified 2026-06-17.