CVE-2026-18119 Concrete CMS - Stored XSS & Privilege Escalation

Concrete CMS < 9.5.3 contains a stored cross-site scripting caused by unsanitized custom style values in the Block Design dialog, letting editor-level users execute scripts in administrator sessions and escalate privileges, exploit requires editor access.

CVSS base score 9.0 /10
Critical
CISA KEV
Not listed
Public exploit
None known
Authentication
Required
EPSS
0.31% chance of exploitation in 30 days
View the NVD record ↗

Details

Type
Stored XSS
Impact
Stored XSS, Privilege Escalation
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H
Published
14 September 2026
Updated
15 October 2026
Weakness
CWE-79

Vendor fix

Update to version 9.5.3 or later.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

References

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