CVE-2026-81902: Concretecms Concrete CMS

High severity, CVSS 8.1. EPSS: 0.2% chance of exploitation in the next 30 days.

Concrete CMS 9 through 9.5.2 did not validate a CSRF token in the orphaned block removal panel action (removeOrphanedBlocks). A remote attacker could craft a request that, when loaded by an authenticated user holding edit permission on the target page, deleted every block on that page's current version; blocks not aliased to another page or scrapbook entry were also removed from the global Blocks table and their block-type data table, permanently destroying the content. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 7.1 with vector CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N. Thanks Yonatan Drori from Tenzai for reporting.

Affected products

• Concretecms Concrete CMS: from 9.0.0, before 9.5.3 (fixed in 9.5.3)

Published 2026-09-14. Last modified 2026-09-18.