High 8.8Published May 1, 2026

CVE-2026-31773Bluetooth: SMP: derive legacy responder STK authentication from MITM state

Updated under an hour ago (Oct 27, 2026, 6:30 AM ET)

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No exploitation reported and no EPSS estimate yet.

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Exploited in the last 30 days

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: 8.8 HIGH (v3.1, CNA)CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness (CWE): CWE-287
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: Linux
NVD analysis: Modified
Record last updated: Oct 19, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

Linux Linux linux:linux (from the name)	from fff3490f47810e2d34b91fb9e31103e923b11c2f before 9a38659a3d06080715691bd3139f9c4b61f688e3; from fff3490f47810e2d34b91fb9e31103e923b11c2f before 667f44f1392df6482483756458c48670e579e9ff; from fff3490f47810e2d34b91fb9e31103e923b11c2f before 929db734d12db41ca5f95424db4612397f1bd4a7; from fff3490f47810e2d34b91fb9e31103e923b11c2f before b1c6a8e554a39b222c0879a288ea98e338fc4d77; from fff3490f47810e2d34b91fb9e31103e923b11c2f before 0afc846bd80073ffcd2b8040f2b2fafaea3d9f72; from fff3490f47810e2d34b91fb9e31103e923b11c2f before 061ee71ac6b03c9f8432fe49538c3682bfcf4cf3; from fff3490f47810e2d34b91fb9e31103e923b11c2f before 9a6d0db176f082685e0b6149700c0baf3ce2aa8b; from fff3490f47810e2d34b91fb9e31103e923b11c2f before 20756fec2f0108cb88e815941f1ffff88dc286fe; and 2 more ranges	CNA record
linux linux_kernel linux:linux_kernel	from 3.15.5 before 3.16; from 3.16.1 before 5.10.253; from 5.11 before 5.15.203; from 5.16 before 6.1.168; from 6.2 before 6.6.134; from 6.7 before 6.12.81; from 6.13 before 6.18.22; from 6.19 before 6.19.12; and 7 more ranges	NVD

References

References

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

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.