From gbhackers.com
A new attack dubbed Bluetooth BIAS attack allows attackers to spoof the already paired device and to successfully authenticate without having the link key that used for pairing.
Researchers from École Polytechnique Fédérale de Lausanne (EPFL) published a paper named BIAS: Bluetooth Impersonation AttackS details that Bluetooth standard contains vulnerabilities enabling an attacker to impersonate a device and to establish a secure connection.