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CVE-2026-81913

Concrete CMS versions 9.5.0 through 9.5.2 are vulnerable to Open Redirect via the rcURL parameter.

CVSS 4.0 5.3 MEDIUMCheck source for fixed versionsKEV status unknown

Original advisory

cve-program · CVE-2026-81913

Published

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.

Read the publisher's advisory

Affected versions, risk and source history

cve-program · CVE-2026-81913

Published

Concrete CMS

https://github.com/concretecms/concretecms

Publisher's version information

Shown as published. These rules are not interpreted as NuGet package version ranges.

{
                    "vendor": "Concrete CMS",
                    "product": "Concrete CMS",
                    "collectionURL": "https://github.com/concretecms/concretecms",
                    "repo": "https://github.com/concretecms/concretecms",
                    "versions": [
                        {
                            "status": "affected",
                            "version": "9.5.0",
                            "lessThanOrEqual": "9.5.2",
                            "versionType": "git"
                        }
                    ],
                    "defaultStatus": "unaffected"
                }

Original source record · Cite this exact observation · Complete original publisher JSON