What is CVE-2026-3240?

CVE-2026-3240 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-2026-3240?

Medium severity. CVSS v3 base score is 4.8 out of 10.

XSS in Concrete Cms

CVE-2026-3240

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 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 minhnn42, namdi and quanlna2 from VCSLab-Viettel Cyber Security for reporting.

Vulnerability class: XSS (Cross-Site Scripting)

Published 2026-03-04 · last modified 2026-06-17.

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 2026-09-30.

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)

CWE-79 — Cross-site Scripting

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-2026-3240?: CVE-2026-3240 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-2026-3240?: Medium severity. CVSS v3 base score is 4.8 out of 10.