CVE-2026-31773

A flaw was found in the Linux kernel's Bluetooth Security Manager Protocol (SMP). The system incorrectly labels a Short Term Key (STK) as authenticated during legacy pairing, even when Man-in-the-Middle (MITM) protection was not established. This misrepresentation of the key's authentication status could allow an attacker to bypass expected security measures, potentially leading to unauthorized access or a downgrade of the Bluetooth connection's security.

Legacy Bluetooth SMP responder STK derivation must incorporate MITM state so pairing strength matches the negotiated threat model. Red Hat treats this as cryptographic protocol correctness for BR/EDR LE legacy pairing.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

To mitigate this issue, prevent the bluetooth module from being loaded. See https://access.redhat.com/solutions/41278 for instructions.