CVE-2026-3240: Concrete CMS has a stored Cross-site Scripting (XSS) vulnerability

March 4, 2026

In Concrete CMS below version 9.4.8, a user with permission to edit a page with element Legacy form can perform a stored XSS attack towards high-privilege accounts via the Question field.

The Concrete CMS security team thanks minhnn42, namdi and quanlna2 from VCSLab-Viettel Cyber Security for reporting.

References

documentation.concretecms.org/9-x/developers/introduction/version-history/948-release-notes
github.com/advisories/GHSA-45fj-fvmm-xcc5
github.com/concretecms/concretecms
github.com/concretecms/concretecms/pull/12826
nvd.nist.gov/vuln/detail/CVE-2026-3240

Code Behaviors & Features

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