Medium severity · published Mar 4, 2026
CVE-2026-3240
Concrete CMS below 9.4.8 is vulnerable to Stored XSS via Legacy form
4.8
CVSS
0.2%
EPSS
No
On KEV
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 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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N
Attack vector
Network
Complexity
Low
Privileges
High
User interaction
Required
Confidentiality
Low
Integrity
Low
Availability
None
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 13% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
CC
Concrete CMS · Concrete CMS
5 before 9.4.8 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-3240
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-3240
Patch
https://documentation.concretecms.org/9-x/developers/introduction/version-history/948-release-notes
Exploit
https://github.com/concretecms/concretecms/pull/12826
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