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4.8
Concrete CMS Stored XSS Allows Attackers to Hijack Admin Accounts
CVE-2026-3240
GHSA-45fj-fvmm-xcc5
Summary
A security weakness in older versions of Concrete CMS lets an attacker with permission to edit a page inject malicious code into the system, potentially allowing them to take control of high-privilege accounts. This could lead to unauthorized changes or data theft. Update to version 9.4.8 or later to patch this issue.
What to do
- Update concrete5 concrete5 to version 9.4.8.
Affected software
| Vendor | Product | Affected versions | Fix available |
|---|---|---|---|
| concrete5 | concrete5 | <= 9.4.8 | 9.4.8 |
| concretecms | concrete_cms | <= 9.4.8 | – |
Original title
Concrete CMS has a stored Cross-site Scripting (XSS) vulnerability
Original description
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.
The Concrete CMS security team thanks minhnn42, namdi and quanlna2 from VCSLab-Viettel Cyber Security for reporting.
nvd CVSS3.1
4.8
nvd CVSS4.0
4.8
Vulnerability type
CWE-79
Cross-site Scripting (XSS)
- https://documentation.concretecms.org/9-x/developers/introduction/version-histor... Release Notes Patch Vendor Advisory
- https://github.com/concretecms/concretecms/pull/12826 Exploit Issue Tracking Vendor Advisory
- https://nvd.nist.gov/vuln/detail/CVE-2026-3240
- https://github.com/advisories/GHSA-45fj-fvmm-xcc5
Published: 4 Mar 2026 · Updated: 13 Mar 2026 · First seen: 6 Mar 2026