CVE-2026-8139: Concretecms Concrete CMS

Medium severity, CVSS 5.4. EPSS: 0.3% chance of exploitation in the next 30 days.

Concrete CMS 9.5.0 and below is vulnerable to Stored XSS via external-link page cvName because updateCollectionAliasExternal bypasses being sanitized. The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of 2.0 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N.  Thanks Yonatan Drori (Tenzai) for reporting.

Affected products

• Concretecms Concrete CMS: up to and including 9.5.0

Published 2026-05-21. Last modified 2026-07-23.