Bluetooth: SMP: derive legacy responder STK authentication from MITM state
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.
- Products
- Kernel
- Affected versions
- Not specified
- Fixed versions
- 5.10.253, 5.15.203, 6.1.168, 6.12.81, 6.18.22, 6.19.12, 6.6.134
- CVEs
- CVE-2026-31773
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 6 Nov 2026, 00:24 UTC · Revision 1
Source evidence
Bluetooth: SMP: derive legacy responder STK authentication from MITM state
core-osv · Original sourcePublished 1 May 2026, 14:15 UTC
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.
osv:CVE-2026-31773
Kernel
Fixed versions: 5.10.253, 5.15.203, 6.1.168, 6.6.134, 6.12.81, 6.18.22, 6.19.12
Complete source record
{
"id": "1d3e039ab3bef90301c65107eadcf06061e42baf17e8ee8e95049cd2cedb5696",
"url": "https://osv.dev/vulnerability/CVE-2026-31773",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "Bluetooth: SMP: derive legacy responder STK authentication from MITM state",
"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.",
"evidence": "osv:CVE-2026-31773",
"products": [
{
"name": {
"value": "Kernel",
"evidence": "/affected/1/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "5.10.253",
"evidence": "/affected/1/ranges"
},
{
"value": "5.15.203",
"evidence": "/affected/1/ranges"
},
{
"value": "6.1.168",
"evidence": "/affected/1/ranges"
},
{
"value": "6.6.134",
"evidence": "/affected/1/ranges"
},
{
"value": "6.12.81",
"evidence": "/affected/1/ranges"
},
{
"value": "6.18.22",
"evidence": "/affected/1/ranges"
},
{
"value": "6.19.12",
"evidence": "/affected/1/ranges"
}
],
"affected_versions": []
}
],
"severity": "high",
"structured": {
"id": "CVE-2026-31773",
"aliases": [
"CVE-2026-31773"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
}
],
"affected": [
{
"ranges": [
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"type": "GIT",
"events": [
{
"introduced": "fff3490f47810e2d34b91fb9e31103e923b11c2f"
},
{
"fixed": "9a38659a3d06080715691bd3139f9c4b61f688e3"
},
{
"fixed": "667f44f1392df6482483756458c48670e579e9ff"
},
{
"fixed": "929db734d12db41ca5f95424db4612397f1bd4a7"
},
{
"fixed": "b1c6a8e554a39b222c0879a288ea98e338fc4d77"
},
{
"fixed": "0afc846bd80073ffcd2b8040f2b2fafaea3d9f72"
},
{
"fixed": "061ee71ac6b03c9f8432fe49538c3682bfcf4cf3"
},
{
"fixed": "9a6d0db176f082685e0b6149700c0baf3ce2aa8b"
},
{
"fixed": "20756fec2f0108cb88e815941f1ffff88dc286fe"
}
]
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"type": "GIT",
"events": [
{
"introduced": "3.15.5"
},
{
"fixed": "3.16"
}
]
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"type": "GIT",
"events": [
{
"introduced": "14ec593d6bb050cf40a4ade2f9ac9ca050e0412c"
}
]
}
],
"versions": [
"v3.15.10",
"v3.15.9",
"v3.15.8",
"v3.15.7",
"v3.15.6",
"v3.15.5"
],
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-31773.json"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "3.16.0"
},
{
"fixed": "5.10.253"
}
]
},
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "5.11.0"
},
{
"fixed": "5.15.203"
}
]
},
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "5.16.0"
},
{
"fixed": "6.1.168"
}
]
},
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "6.2.0"
},
{
"fixed": "6.6.134"
}
]
},
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "6.7.0"
},
{
"fixed": "6.12.81"
}
]
},
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "6.13.0"
},
{
"fixed": "6.18.22"
}
]
},
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "6.19.0"
},
{
"fixed": "6.19.12"
}
]
}
],
"package": {
"name": "Kernel",
"ecosystem": "Linux"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-31773.json"
}
}
],
"modified": "2026-10-28T02:30:45.399184825Z",
"provider": "osv",
"references": [
"https://git.kernel.org/stable/c/061ee71ac6b03c9f8432fe49538c3682bfcf4cf3",
"https://git.kernel.org/stable/c/0afc846bd80073ffcd2b8040f2b2fafaea3d9f72",
"https://git.kernel.org/stable/c/20756fec2f0108cb88e815941f1ffff88dc286fe",
"https://git.kernel.org/stable/c/667f44f1392df6482483756458c48670e579e9ff",
"https://git.kernel.org/stable/c/929db734d12db41ca5f95424db4612397f1bd4a7",
"https://git.kernel.org/stable/c/9a38659a3d06080715691bd3139f9c4b61f688e3",
"https://git.kernel.org/stable/c/9a6d0db176f082685e0b6149700c0baf3ce2aa8b",
"https://git.kernel.org/stable/c/b1c6a8e554a39b222c0879a288ea98e338fc4d77",
"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31773.json",
"https://nvd.nist.gov/vuln/detail/CVE-2026-31773",
"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
],
"provider_metadata": {
"cna_assigner": "Linux",
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31773.json"
}
},
"related_cves": [
{
"value": "CVE-2026-31773",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 513460,
"published_at": "2026-05-01T14:15:01.277+00:00"
}