CVE-2026-31773
Bluetooth: SMP: derive legacy responder STK authentication from MITM state
Description
In the Linux kernel, the following vulnerability has been resolved: Bluetooth: SMP: derive legacy responder STK authentication from MITM state The legacy responder path in smp_random() currently labels the stored STK as authenticated whenever pending_sec_level is BT_SECURITY_HIGH. That reflects what the local service requested, not what the pairing flow actually achieved. For Just Works/Confirm legacy pairing, SMP_FLAG_MITM_AUTH stays clear and the resulting STK should remain unauthenticated even if the local side requested HIGH security. Use the established MITM state when storing the responder STK so the key metadata matches the pairing result. This also keeps the legacy path aligned with the Secure Connections code, which already treats JUST_WORKS/JUST_CFM as unauthenticated.
INFO
Published Date :
May 1, 2026, 3:16 p.m.
Last Modified :
May 1, 2026, 3:24 p.m.
Remotely Exploit :
No
Source :
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Affected Products
The following products are affected by CVE-2026-31773
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
Solution
- Update the Linux kernel.
- Apply the patch for Bluetooth SMP.
- Use established MITM state for responder STK.
- Align legacy path with Secure Connections code.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-31773.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-31773 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-31773
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-31773 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-31773 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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New CVE Received by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
May. 01, 2026
Action Type Old Value New Value Added Description In the Linux kernel, the following vulnerability has been resolved: Bluetooth: SMP: derive legacy responder STK authentication from MITM state The legacy responder path in smp_random() currently labels the stored STK as authenticated whenever pending_sec_level is BT_SECURITY_HIGH. That reflects what the local service requested, not what the pairing flow actually achieved. For Just Works/Confirm legacy pairing, SMP_FLAG_MITM_AUTH stays clear and the resulting STK should remain unauthenticated even if the local side requested HIGH security. Use the established MITM state when storing the responder STK so the key metadata matches the pairing result. This also keeps the legacy path aligned with the Secure Connections code, which already treats JUST_WORKS/JUST_CFM as unauthenticated. Added Reference https://git.kernel.org/stable/c/061ee71ac6b03c9f8432fe49538c3682bfcf4cf3 Added Reference https://git.kernel.org/stable/c/0afc846bd80073ffcd2b8040f2b2fafaea3d9f72 Added Reference https://git.kernel.org/stable/c/20756fec2f0108cb88e815941f1ffff88dc286fe Added Reference https://git.kernel.org/stable/c/667f44f1392df6482483756458c48670e579e9ff Added Reference https://git.kernel.org/stable/c/929db734d12db41ca5f95424db4612397f1bd4a7 Added Reference https://git.kernel.org/stable/c/9a38659a3d06080715691bd3139f9c4b61f688e3 Added Reference https://git.kernel.org/stable/c/9a6d0db176f082685e0b6149700c0baf3ce2aa8b Added Reference https://git.kernel.org/stable/c/b1c6a8e554a39b222c0879a288ea98e338fc4d77