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CVE-2026-85385

9.6 CRITICAL

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

AI risk analysis

Summary
The vulnerability allows a stored cross-site scripting (XSS) payload to be executed in an administrator's browser, leading to potential session hijacking and unauthorized actions.
Exploitability
Exploitation requires the concrete.misc.user_timezones feature to be enabled and, for unauthenticated access, public registration to be enabled as well. The vulnerability is relatively hard to exploit without these preconditions.
Blast radius
If exploited, the impact is high, as it can lead to full administrative control over the site, including reading CSRF tokens, creating administrator accounts, or changing site settings.
Detection
No reliable host or network indicator is derivable from the published description.
Prioritized remediation
Upgrade to Concrete CMS 9.5.4 or later.
xsswebadmincms

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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