KNOB Security Flaw Exploits All Versions Of Bluetooth Devices. It provides the capability to dilute the effectiveness of encryption of Bluetooth devices through shortening the length of the encryption key to just a single octet. A simple brute-force attack will be enough to break the otherwise secure Bluetooth encryption process. The bug was demonstrated publicly in the currently ongoing (at the time of this writing) USENIX Security Symposium. The good news though is that it is not easy to exploit.”]
Source: https://hackercombat.com/knob-security-flaw-exploits-all-versions-of-bluetooth-devices/