CVE-2026-81913
Published:September 11, 2026
Updated:September 22, 2026
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.
Affected Packages
https://github.com/concretecms/concretecms.git (GITHUB):
Affected version(s) >=9.5.0 <9.5.3Fix Suggestion:
Update to version 9.5.3concrete5/core (PHP):
Affected version(s) >=9.5.0 <9.5.3Fix Suggestion:
Update to version 9.5.3concrete5/concrete5 (PHP):
Affected version(s) >=9.5.0 <9.5.3Fix Suggestion:
Update to version 9.5.3Related Resources (1)
Do you need more information?
Contact UsCVSS v4
Base Score:
5.3
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
NONE
User Interaction
PASSIVE
Vulnerable System Confidentiality
NONE
Vulnerable System Integrity
LOW
Vulnerable System Availability
NONE
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
4.3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality
NONE
Integrity
LOW
Availability
NONE
Weakness Type (CWE)
URL Redirection to Untrusted Site ('Open Redirect')
EPSS
Base Score:
0.59