KNOB (Key Negotiation Of Bluetooth) - Weakness in the Bluetooth wireless standard that could allow hackers to intercept keystrokes, address books, and other sensitive data

The attack forces two or more devices to choose an encryption key just a single byte in length before establishing a Bluetooth connection. Attackers within radio range can then use commodity hardware to quickly crack the key

KNOB doesn't require an attacker to have any previously shared secret material or to observe the pairing process of the targeted devices. The exploit is invisible to Bluetooth apps and the operating system they run on, making the attack almost impossible to detect without highly specialized equipment.

https://news.hitb.org/content/new-attack-exploiting-serious-bluetooth-weakness-can-intercept-sensitive-data