Bluetooth: SMP: derive legacy responder STK authentication from MITM state

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Summary

CVECVE-2026-31773
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-05-01 15:16:40 UTC
Updated2026-05-03 07:16:20 UTC
DescriptionIn 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.

Risk And Classification

Primary CVSS: v3.1 8.8 HIGH from 416baaa9-dc9f-4396-8d5f-8c081fb06d67

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

EPSS: 0.000460000 probability, percentile 0.139200000 (date 2026-05-02)

VersionSourceTypeScoreSeverityVector
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary8.8HIGHCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
3.1CNADECLARED8.8HIGHCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Adjacent
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected fff3490f47810e2d34b91fb9e31103e923b11c2f 9a38659a3d06080715691bd3139f9c4b61f688e3 git Not specified
CNA Linux Linux affected fff3490f47810e2d34b91fb9e31103e923b11c2f 667f44f1392df6482483756458c48670e579e9ff git Not specified
CNA Linux Linux affected fff3490f47810e2d34b91fb9e31103e923b11c2f 929db734d12db41ca5f95424db4612397f1bd4a7 git Not specified
CNA Linux Linux affected fff3490f47810e2d34b91fb9e31103e923b11c2f b1c6a8e554a39b222c0879a288ea98e338fc4d77 git Not specified
CNA Linux Linux affected fff3490f47810e2d34b91fb9e31103e923b11c2f 0afc846bd80073ffcd2b8040f2b2fafaea3d9f72 git Not specified
CNA Linux Linux affected fff3490f47810e2d34b91fb9e31103e923b11c2f 061ee71ac6b03c9f8432fe49538c3682bfcf4cf3 git Not specified
CNA Linux Linux affected fff3490f47810e2d34b91fb9e31103e923b11c2f 9a6d0db176f082685e0b6149700c0baf3ce2aa8b git Not specified
CNA Linux Linux affected fff3490f47810e2d34b91fb9e31103e923b11c2f 20756fec2f0108cb88e815941f1ffff88dc286fe git Not specified
CNA Linux Linux affected 14ec593d6bb050cf40a4ade2f9ac9ca050e0412c git Not specified
CNA Linux Linux affected 3.16 Not specified
CNA Linux Linux unaffected 3.16 semver Not specified
CNA Linux Linux unaffected 5.10.253 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.203 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.168 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.134 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.81 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.22 6.18.* semver Not specified
CNA Linux Linux unaffected 6.19.12 6.19.* semver Not specified
CNA Linux Linux unaffected 7.0 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/9a6d0db176f082685e0b6149700c0baf3ce2aa8b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/9a38659a3d06080715691bd3139f9c4b61f688e3 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/061ee71ac6b03c9f8432fe49538c3682bfcf4cf3 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/b1c6a8e554a39b222c0879a288ea98e338fc4d77 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/929db734d12db41ca5f95424db4612397f1bd4a7 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/667f44f1392df6482483756458c48670e579e9ff 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/20756fec2f0108cb88e815941f1ffff88dc286fe 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/0afc846bd80073ffcd2b8040f2b2fafaea3d9f72 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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