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CVE-2026-81913 Details

Description

Concrete CMS versions 9.5.0 through 9.5.2 are vulnerable to Open Redirect via the rcURL parameter. An attacker can craft a single link on the site's own domain that sends a user to an arbitrary external site immediately after authentication, facilitating phishing and credential theft. The same handling is present in the registration flow, giving a second entry point on sites with registration enabled. Concrete CMS versions prior to 9.5.0 do not include the rcURL parameter or this allowlist and are not affected. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 5.3 with vector CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N. Thanks Michal M. for reporting.

Metrics

CVSS 3.x Severity and Vector Strings:

NIST: [email protected]CVSS-B:6.1 MEDIUMVector:CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

References to Advisories, Solutions, and Tools

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URL	Source(s)	Tag(s)
https://documentation.concretecms.org/developers/introduction/version-history/953-release-notes	ConcreteCMS	Broken Link

Weakness Enumeration

CWE-ID	CWE Name	Source
CWE-601	URL Redirection to Untrusted Site ('Open Redirect')	ConcreteCMS

Affected Products

Product	Versions
concretecms concrete cms	>= 9.5.0, < 9.5.3
CPE cpe:2.3:a:concretecms:concrete_cms:::::::: Remediation No remediation found in references.

Change History

3 change records found show changes

Date	Action	Recorded By
Sep 24, 2026	Initial Analysis	[email protected]
Sep 11, 2026	New CVE Received	ConcreteCMS
Sep 11, 2026	CVE Modified	CISA-ADP