CVE-2026-31773

Adjacent authentication bypass via misclassified Bluetooth STK

Published May 1, 2026 · Updated May 1, 2026

Bluetooth SMP authentication bypass in affected Linux Kernel releases allows physically proximate attackers to obtain authenticated link state. In the legacy responder path, smp_random() marks the stored short-term key as authenticated from pending_sec_level instead of SMP_FLAG_MITM_AUTH, even when Just Works or Confirm pairing provided no MITM authentication. Exploitation requires Bluetooth pairing within radio range while a local service requests high security, after which the mismarked key can satisfy authentication-dependent access checks.

CVSS severity8.8
High
EPSS probability0.28%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Bluetooth SMP authentication bypass in affected Linux Kernel releases allows physically proximate attackers to obtain authenticated link state. In the legacy responder path, smp_random() marks the stored short-term key as authenticated from pending_sec_level instead of SMP_FLAG_MITM_AUTH, even when Just Works or Confirm pairing provided no MITM authentication. Exploitation requires Bluetooth pairing within radio range while a local service requests high security, after which the mismarked key can satisfy authentication-dependent access checks.

The record

CVE
CVE-2026-31773
Published
May 1, 2026
Updated
May 1, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
Unavailable
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 1, 2026CVE publishedPublication date reported by the CVE source.
  2. May 1, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=14ec593d6bb050cf40a4ade2f9ac9ca050e0412c
  2. Affected versionversion=3.16
  3. Affected versionversion=fff3490f47810e2d34b91fb9e31103e923b11c2f <061ee71ac6b03c9f8432fe49538c3682bfcf4cf3
  4. Affected versionversion=fff3490f47810e2d34b91fb9e31103e923b11c2f <0afc846bd80073ffcd2b8040f2b2fafaea3d9f72
  5. Affected versionversion=fff3490f47810e2d34b91fb9e31103e923b11c2f <20756fec2f0108cb88e815941f1ffff88dc286fe
  6. Affected versionversion=fff3490f47810e2d34b91fb9e31103e923b11c2f <667f44f1392df6482483756458c48670e579e9ff
  7. Affected versionversion=fff3490f47810e2d34b91fb9e31103e923b11c2f <929db734d12db41ca5f95424db4612397f1bd4a7
  8. Affected versionversion=fff3490f47810e2d34b91fb9e31103e923b11c2f <9a38659a3d06080715691bd3139f9c4b61f688e3
  9. Affected versionversion=fff3490f47810e2d34b91fb9e31103e923b11c2f <9a6d0db176f082685e0b6149700c0baf3ce2aa8b
  10. Affected versionversion=fff3490f47810e2d34b91fb9e31103e923b11c2f <b1c6a8e554a39b222c0879a288ea98e338fc4d77

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=14ec593d6bb050cf40a4ade2f9ac9ca050e0412c; version=3.16; version=fff3490f47810e2d34b91fb9e31103e923b11c2f <061ee71ac6b03c9f8432fe49538c3682bfcf4cf3; version=fff3490f47810e2d34b91fb9e31103e923b11c2f <0afc846bd80073ffcd2b8040f2b2fafaea3d9f72; version=fff3490f47810e2d34b91fb9e31103e923b11c2f <20756fec2f0108cb88e815941f1ffff88dc286fe; version=fff3490f47810e2d34b91fb9e31103e923b11c2f <667f44f1392df6482483756458c48670e579e9ff; version=fff3490f47810e2d34b91fb9e31103e923b11c2f <929db734d12db41ca5f95424db4612397f1bd4a7; version=fff3490f47810e2d34b91fb9e31103e923b11c2f <9a38659a3d06080715691bd3139f9c4b61f688e3; version=fff3490f47810e2d34b91fb9e31103e923b11c2f <9a6d0db176f082685e0b6149700c0baf3ce2aa8b; version=fff3490f47810e2d34b91fb9e31103e923b11c2f <b1c6a8e554a39b222c0879a288ea98e338fc4d77

Published CVSS scores

8.8LinuxCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

No sourced classifications are available.

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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