Bluetooth: MSFT: validate evt_prefix_len against the response length

{
  "id": "bd709901b8cfcdc8919cb8829cff852ae53ff34ddd2e5135dd488fc43d86f088",
  "url": "https://osv.dev/vulnerability/CVE-2026-90251",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Bluetooth: MSFT: validate evt_prefix_len against the response length",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: Bluetooth: MSFT: validate evt_prefix_len against the response length read_supported_features() only checks that the response covers the fixed part of struct msft_rp_read_supported_features, which is 11 bytes: if (skb->len < sizeof(*rp)) { bt_dev_err(hdev, \"MSFT supported features length mismatch\"); goto failed; } evt_prefix[] is a flexible array member and rp->evt_prefix_len is an unvalidated u8 taken straight out of that response, so msft->evt_prefix = kmemdup(rp->evt_prefix, rp->evt_prefix_len, GFP_KERNEL); copies up to 255 bytes from a reply that may have carried none of them. What is copied is data the controller never sent, and it is then used to match incoming vendor events in msft_vendor_evt(). This is not an out-of-bounds access. An skb data allocation always has at least SKB_DATA_ALIGN(sizeof(struct skb_shared_info)) bytes past the payload, which is more than the 255 byte maximum, so the read stays inside the allocation and KASAN does not report it. It is still a read of bytes the host was never given, with the length fully controlled by the controller. Reject a response that is too short for the prefix it declares. Verified with an emulated controller over /dev/vhci on a KASAN kernel, with vhci made to advertise an MSFT opcode the way btintel, btqca, btmtk and btrtl do unconditionally. A reply of exactly 11 bytes declaring evt_prefix_len = 255 reaches kmemdup and copies 255 bytes (\"skb->len=11 evt_p",
    "evidence": "osv:CVE-2026-90251",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "5.10.270",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "5.15.221",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.1.188",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.6.157",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.12.110",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.52",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.2.6",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-90251",
      "aliases": [
        "CVE-2026-90251"
      ],
      "affected": [
        {
          "ranges": [
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              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
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                {
                  "fixed": "dce783a10e70f013410f5b583a29fc3286899629"
                },
                {
                  "fixed": "21f539c59ed330b671d75fd119c5f659ff92fbd1"
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                {
                  "fixed": "52b1b3b4d403cbda1b70ce2385e1a71f166a87ba"
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                {
                  "fixed": "e804d54a5a99d99250490e68093eff7190472e6f"
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                {
                  "fixed": "620c2631cff490d14d0b9d56f185cc745806d6d7"
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                  "fixed": "7c2658023d839b651368a5b8b781bf9a817647cb"
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            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-90251.json"
          }
        },
        {
          "ranges": [
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              "type": "ECOSYSTEM",
              "events": [
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                  "introduced": "5.8.0"
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                {
                  "fixed": "5.10.270"
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          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
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          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-90251.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:33.019454103Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/0079e1a944634ab2dc1c7cdec1144486d096407e",
        "https://git.kernel.org/stable/c/21f539c59ed330b671d75fd119c5f659ff92fbd1",
        "https://git.kernel.org/stable/c/52b1b3b4d403cbda1b70ce2385e1a71f166a87ba",
        "https://git.kernel.org/stable/c/620c2631cff490d14d0b9d56f185cc745806d6d7",
        "https://git.kernel.org/stable/c/63562cfaea8a650fdb31ee8de21c32e3600be642",
        "https://git.kernel.org/stable/c/7c2658023d839b651368a5b8b781bf9a817647cb",
        "https://git.kernel.org/stable/c/dce783a10e70f013410f5b583a29fc3286899629",
        "https://git.kernel.org/stable/c/e804d54a5a99d99250490e68093eff7190472e6f",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/90xxx/CVE-2026-90251.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-90251",
        "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/2026/90xxx/CVE-2026-90251.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-90251",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 500193,
  "published_at": "2026-09-17T16:07:52.066+00:00"
}