pam_usb, a Linux PAM module that uses removable media for authentication, allows a NULL pointer dereference when udisks_drive_get_serial(), udisks_drive_get_vendor(), or udisks_drive_get_model() returns NULL. The returned NULL is passed directly to strcmp() without checking, leading to SIGSEGV and a PAM crash. The crash prevents the authentication stack from completing, effectively denying a user from logging in for that session.

The vulnerability affects the mcdope pam_usb product in all releases before version 0.8.7. No other vendors or products are listed as affected.

The CVSS score of 4.6 classifies this as a moderate severity issue. EPSS data is not available, and the vulnerability is not listed in the CISA KEV catalog. The likely attack vector is local: an attacker who can insert a USB device or emulate one can trigger the crash during a user’s authentication attempt, causing a brief denial-of-service. No remote code execution or privilege escalation is described in the CVE.