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)
Published · last modified .
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.
EPSS exploit prediction
EPSS: 0.003 (17.0th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 17th percentile — 17.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.003 · change: +0.001
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.