Reachy Mini Bluetooth PIN authentication can be bypassed by racing an authenticated device

Summary

The Reachy Mini Bluetooth service asks a connecting device for a PIN before it will accept commands. The check protects the session but not the caller, so an attacker in Bluetooth range can ride along on someone else's successful authentication. The authenticated state is kept in a single shared flag on the service instance rather than per device. BlueZ passes the calling device's identity to the characteristic write handler in the options argument, but WriteValue(self, value, options) in src/reachy_mini/daemon/app/services/bluetooth/bluetooth_service.py ignores options entirely. The handler therefore has no idea which device sent a given write, and it cannot tell the authenticated one from any other. Once any device completes the PIN exchange, the flag is set and every nearby device can send CMD_ commands until it resets. An attacker simply waits within radio range for a legitimate user to authenticate, then writes commands into the same window. No PIN is ever guessed or brute-forced. This is the second step of a three-step chain that JFrog documented against the robot. The first is the unrestricted file upload in the media sounds API, tracked as CVE-2026-55419, which places an attacker-controlled script on the filesystem. This issue then provides command access over Bluetooth. The third is the Bluetooth command handler path traversal, tracked as CVE-2026-62661, which runs that script as root.