This vulnerability affects the generate_auth_token function in the cps/kobo_auth.py file of janeczku Calibre-Web versions up to 0.6.26. Improper authorization arises from the ability to manipulate the user_id argument, potentially allowing unauthorized access or actions. The attack vector is remote with no privileges or user interaction required. The CVSS 4.0 base score is 5.3, reflecting medium severity with network attack vector, low complexity, and no privileges required. The vendor was contacted but has not provided a fix or advisory, and no official remediation is currently available.

Successful exploitation could allow an attacker to bypass authorization controls by manipulating the user_id parameter, potentially gaining unauthorized access or performing unauthorized actions within the affected Calibre-Web instance. The impact is limited to the scope of authorization bypass and does not indicate direct code execution or data corruption. No known exploits in the wild have been reported, but a public exploit exists.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Since no official fix or advisory has been released by the vendor, users should monitor for updates from janeczku. Until a patch is available, consider restricting network access to the Calibre-Web service and applying compensating controls to limit exposure. Avoid exposing the service to untrusted networks where possible.