CVE-2026-85385: Concretecms Concrete CMS cross-site scripting (XSS) (CVSS 9.6)

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 3.1 breakdown

Attack vectorNetwork

Attack complexityLow

Privileges requiredNone

User interactionRequired

ScopeChanged

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

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

Affected products

Concretecms Concrete CMS< 9.5.4

Remediation

Fixed in

Concretecms Concrete CMS≥ 9.5.4

References

https://documentation.concretecms.org/developers/introduction/version-history/954-release-notesBroken Link

Related CVEs

Recent high-severity vulnerabilities sharing a weakness type.

Frequently asked

Is CVE-2026-85385 being actively exploited?

CVE-2026-85385 is not in the CISA KEV catalog. Its EPSS exploit probability is 0.50%.

How severe is CVE-2026-85385?

CVE-2026-85385 has a CVSS 3.1 base score of 9.6, rated critical. EPSS estimates a 0.50% probability of exploitation.

Which products are affected by CVE-2026-85385?

Affected products include Concretecms Concrete CMS.

How do I fix CVE-2026-85385?

Upgrade affected software to a fixed version, for example Concretecms Concrete CMS 9.5.4 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-85385 against the real software inventory on every managed device, every day. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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