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CVE-2026-85385

9.6 CRITICAL

Published 2026-09-16 · Updated 2026-09-21

AI risk analysis

Summary
A stored cross-site scripting vulnerability in Concrete CMS versions below 9.5.4 allowed attackers to execute scripts in an administrator's browser by manipulating timezone settings.
Exploitability
Exploitation required enabling specific features and was moderately difficult, as it needed concrete.misc.user_timezones to be enabled and public registration for the unauthenticated path.
Blast radius
If exploited, this could lead to severe consequences such as reading CSRF tokens, creating administrator accounts, or changing site settings in an administrator's session.
Prioritized remediation
Update Concrete CMS to version 9.5.4 or later to mitigate this vulnerability.
xsswebcmsadmin

Analysis generated locally by qwen2.5:7b-instruct (no data left the box). AI-assisted — verify against primary sources before acting.

NVD description

Concrete CMS below 9.5.4 did not validate the user timezone value (uTimezone) on write and rendered it without output encoding on the Dashboard user management page, where Date::getTimezoneDisplayName() returns any non-IANA value unchanged. A stored cross-site scripting payload saved in this field executed in an administrator's browser when they viewed the affected user in the Dashboard, running script in the admin session (for example to read CSRF tokens, create administrator accounts, or change site settings). In Concrete CMS 9.5.3 the field became reachable by unauthenticated visitors through public registration; in Concrete CMS below 9.5.3, the same field was reachable by any authenticated user through the account profile editor. Exploitation required concrete.misc.user_timezones to be enabled (off by default), and the unauthenticated path additionally required public registration to be enabled. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 7.7 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N. Thanks Suraj Bhosale for reporting.

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H

Weaknesses

CWE-79

Vendors

concretecms

Products

concrete cms

All references

Source data: NVD (nvd.nist.gov), public domain. Exploit-DB.ai adds local AI analysis for defensive use only.

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