Bluetooth BR/EDR devices with Secure Simple Pairing and Secure Connections pairing in Bluetooth Core Specification 4.2 through 5.4 allow certain man-in-the-middle attacks that force a short key length, and might lead to discovery of the encryption key and live injection, aka BLUFFS.
Refer: https://www.bluetooth.com/learn-about-bluetooth/key-attributes/bluetooth-security/bluffs-vulnerability/
An information leakage vulnerability in the Bluetooth Low Energy advertisement scan response in Bluetooth Core Specifications 4.0 through 5.2, and extended scan response in Bluetooth Core Specifications 5.0 through 5.2, may be used to identify devices using Resolvable Private Addressing (RPA) by their response or non-response to specific scan requests from remote addresses. RPAs that have been associated with a specific remote device may also be used to identify a peer in the same manner by using its reaction to an active scan request. This has also been called an allowlist-based side channel.
Bluetooth® Low Energy Pairing in Bluetooth Core Specification v4.0 through v5.3 may permit an unauthenticated MITM to acquire credentials with two pairing devices via adjacent access when the MITM negotiates Legacy Passkey Pairing with the pairing Initiator and Secure Connections Passkey Pairing with the pairing Responder and brute forces the Passkey entered by the user into the Initiator. The MITM attacker can use the identified Passkey value to complete authentication with the Responder via Bluetooth pairing method confusion.
Bluetooth® Pairing in Bluetooth Core Specification v1.0B through v5.3 may permit an unauthenticated MITM to acquire credentials with two pairing devices via adjacent access when at least one device supports BR/EDR Secure Connections pairing and the other BR/EDR Legacy PIN code pairing if the MITM negotiates BR/EDR Secure Simple Pairing in Secure Connections mode using the Passkey association model with the pairing Initiator and BR/EDR Legacy PIN code pairing with the pairing Responder and brute forces the Passkey entered by the user into the Responder as a 6-digit PIN code. The MITM attacker can use the identified PIN code value as the Passkey value to complete authentication with the Initiator via Bluetooth pairing method confusion.
Bluetooth Classic in Bluetooth Core Specification through 5.3 does not properly conceal device information for Bluetooth transceivers in Non-Discoverable mode. By conducting an efficient over-the-air attack, an attacker can fully extract the permanent, unique Bluetooth MAC identifier, along with device capabilities and identifiers, some of which may contain identifying information about the device owner. This additionally allows the attacker to establish a connection to the target device.
Devices supporting Bluetooth before 5.1 may allow man-in-the-middle attacks, aka BLURtooth. Cross Transport Key Derivation in Bluetooth Core Specification v4.2 and v5.0 may permit an unauthenticated user to establish a bonding with one transport, either LE or BR/EDR, and replace a bonding already established on the opposing transport, BR/EDR or LE, potentially overwriting an authenticated key with an unauthenticated key, or a key with greater entropy with one with less.
Mesh Provisioning in the Bluetooth Mesh profile 1.0 and 1.0.1 may permit a nearby device, able to conduct a successful brute-force attack on an insufficiently random AuthValue before the provisioning procedure times out, to complete authentication by leveraging Malleable Commitment.
Unencrypted Bluetooth Low Energy baseband links in Bluetooth Core Specifications 4.0 through 5.2 may permit an adjacent device to inject a crafted packet during the receive window of the listening device before the transmitting device initiates its packet transmission to achieve full MITM status without terminating the link. When applied against devices establishing or using encrypted links, crafted packets may be used to terminate an existing link, but will not compromise the confidentiality or integrity of the link.