XSS in Concrete Cms
CVE-2026-3241
In Concrete CMS below version 9.4.8, a stored cross-site scripting (XSS) vulnerability exists in the "Legacy Form" block. An authenticated user with permissions to create or edit forms (e.g., a rogue administrator) can inject a persistent JavaScript payload into the options of a multiple-choice question (Checkbox List, Radio Buttons, or Select Box). This payload is then executed in the browser of any user who views the page containing the form. The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of 4.8 with vector CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N. Thanks M3dium for reporting.
Vulnerability class: XSS (Cross-Site Scripting)
EPSS: 0.002 (11.2th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 4.8 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N.
Affected products
- Concrete Cms — versions 5
- Concretecms Concrete_cms
Weakness classification (CWE)
References
- ff5b8ace-8b95-4078-9743-eac1ca5451de (Exploit, Issue Tracking, Vendor Advisory)
- ff5b8ace-8b95-4078-9743-eac1ca5451de (Patch, Release Notes, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-3241?
- CVE-2026-3241 is a medium-severity vulnerability in Concrete Cms, classified under Cross-site Scripting. CVSS score: 4.8/10. Published 2026-03-04.
- How severe is CVE-2026-3241?
- Medium severity. CVSS v3 base score is 4.8 out of 10.