FKIE_CVE-2026-31773

Vulnerability from fkie_nvd - Published: 2026-05-01 15:16 - Updated: 2026-05-03 07:16
Severity ?
8.8 (High) - CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Summary
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.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/061ee71ac6b03c9f8432fe49538c3682bfcf4cf3
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/0afc846bd80073ffcd2b8040f2b2fafaea3d9f72
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/20756fec2f0108cb88e815941f1ffff88dc286fe
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/667f44f1392df6482483756458c48670e579e9ff
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/929db734d12db41ca5f95424db4612397f1bd4a7
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/9a38659a3d06080715691bd3139f9c4b61f688e3
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/9a6d0db176f082685e0b6149700c0baf3ce2aa8b
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/b1c6a8e554a39b222c0879a288ea98e338fc4d77
Impacted products
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{
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nBluetooth: SMP: derive legacy responder STK authentication from MITM state\n\nThe legacy responder path in smp_random() currently labels the stored\nSTK as authenticated whenever pending_sec_level is BT_SECURITY_HIGH.\nThat reflects what the local service requested, not what the pairing\nflow actually achieved.\n\nFor Just Works/Confirm legacy pairing, SMP_FLAG_MITM_AUTH stays clear\nand the resulting STK should remain unauthenticated even if the local\nside requested HIGH security. Use the established MITM state when\nstoring the responder STK so the key metadata matches the pairing result.\n\nThis also keeps the legacy path aligned with the Secure Connections code,\nwhich already treats JUST_WORKS/JUST_CFM as unauthenticated."
    }
  ],
  "id": "CVE-2026-31773",
  "lastModified": "2026-05-03T07:16:20.700",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "ADJACENT_NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 8.8,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 2.8,
        "impactScore": 5.9,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-05-01T15:16:40.587",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/061ee71ac6b03c9f8432fe49538c3682bfcf4cf3"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/0afc846bd80073ffcd2b8040f2b2fafaea3d9f72"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/20756fec2f0108cb88e815941f1ffff88dc286fe"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/667f44f1392df6482483756458c48670e579e9ff"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/929db734d12db41ca5f95424db4612397f1bd4a7"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/9a38659a3d06080715691bd3139f9c4b61f688e3"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/9a6d0db176f082685e0b6149700c0baf3ce2aa8b"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/b1c6a8e554a39b222c0879a288ea98e338fc4d77"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Awaiting Analysis"
}


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