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Vulnerability record · CVE-2026-31773 · published 1 May 2026

CVE-2026-31773: Linux kernel vulnerability

Linux · Linux Kernel

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.

8.8 CVSS 3.1 High EPSS 0.46% · top 62.9%
8.8CVSS 3.1 base score
0.46%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
8References
17 Jun 2026Last modified by NVD

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.

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://git.kernel.org/stable/c/061ee71ac6b03c9f8432fe49538c3682bfcf4cf3 Patch
https://git.kernel.org/stable/c/0afc846bd80073ffcd2b8040f2b2fafaea3d9f72 Patch
https://git.kernel.org/stable/c/20756fec2f0108cb88e815941f1ffff88dc286fe Patch
https://git.kernel.org/stable/c/667f44f1392df6482483756458c48670e579e9ff Patch
https://git.kernel.org/stable/c/929db734d12db41ca5f95424db4612397f1bd4a7 Patch
https://git.kernel.org/stable/c/9a38659a3d06080715691bd3139f9c4b61f688e3 Patch
https://git.kernel.org/stable/c/9a6d0db176f082685e0b6149700c0baf3ce2aa8b Patch
https://git.kernel.org/stable/c/b1c6a8e554a39b222c0879a288ea98e338fc4d77 Patch

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Source: NIST National Vulnerability Database (record CVE-2026-31773), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.