CVE-2026-31773
Description
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.
Statement
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.
Mitigation
To mitigate this issue, prevent the bluetooth module from being loaded. See https://access.redhat.com/solutions/41278 for instructions.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.5 | N/A | 8.8 |
| Attack Vector | Local | N/A | Adjacent Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | Low | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | High |
| Integrity Impact | None | N/A | High |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Understanding the Weakness (CWE)
Integrity,Other
Technical Impact: Unexpected State; Alter Execution Logic
This weakness could place the system in a state that could lead unexpected logic to be executed or other unintended behaviors.
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