Login Request a demo
Critical severity · published Sep 14, 2026
CVE-2026-18119
Concrete CMS below 9.5.3 is vulnerable to Stored XSS via unsanitized inline block custom style values
9.0
CVSS
0.5%
EPSS
No
On KEV
Description
Concrete CMS below 9.5.3 did not sanitize custom style values in the Block Design dialog before writing them into page CSS via a DOM sink, permitting stored cross-site scripting. An editor-level user could execute script in an administrator's session and escalate privileges. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 7.0 with vector CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:P/VC:L/VI:H/VA:H/SC:N/SI:N/SA:N. Thanks Nguyen Manh Thuan for reporting.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
Required
Confidentiality
High
Integrity
High
Availability
High
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)0.5% · higher than 40% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
CC
Concrete CMS · Concrete CMS
5.0.0 through 9.5.2 · source: vendor, NVD
Affected product
CC
Concrete CMS
Concrete CMS
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-18119
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-18119
Broken Link
https://documentation.concretecms.org/developers/introduction/version-history/953-release-notes
More from Concrete CMS
9.6
CVE-2026-85385
Concrete CMS below 9.5.4 is vulnerable to Stored XSS via User Timezone Field
8.8
CVE-2026-8409
Concrete CMS 9 before 9.5.0 is vulnerable to Cross Site Request Forgery (CSRF) at concrete/controllers/dialog/logs/delete
8.8
CVE-2026-8410
Concrete CMS 9 before 9.5.0 is vulnerable to Cross Site Request Forgery (CSRF) at concrete/controllers/dialog/logs/bulk/delete
8.8
CVE-2026-8411
Concrete CMS 9 before 9.5.0 is vulnerable to Cross Site Request Forgery (CSRF) at concrete/controllers/dialog/page/bulk/delete
8.8
CVE-2026-8412
Concrete CMS 9 before 9.5.0 is vulnerable to Cross Site Request Forgery (CSRF) at concrete/controllers/dialog/page/bulk/cache