CVE-2026-81906

MEDIUM CVSS 4.0: 6.3 EPSS 0.34%
Updated Sep 11, 2026
Concrete
Parameter Value
CVSS 6.3 (MEDIUM)
Affected Versions before 9.5.3
Type CWE-288 (Authentication Bypass Using Alternate Path)
Vendor Concrete
Public PoC No

Concrete CMS OAuth callback login path prior to version 9.5.3 did not check whether an account was active or email-validated before establishing a session. A deactivated or unvalidated user with an existing OAuth binding could complete authentication and receive a session that was fully authenticated for the callback response, with the login recorded and login events dispatched. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 6.3 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N.

Thanks Yonatan Drori from Tenzai for reporting.

Attack Parameters

Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Attack Requirements
Present
Additional conditions required
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed

Impact Assessment

Confidentiality
None
No data leak
Integrity
Low
Partial data modification
Availability
None
No disruption

CVSS Vector v4.0

Vulnerable Products

concrete cms:concrete cms