Bluetooth: eir: Fix stack OOB write when prepending the Flags AD

{
  "id": "231359a480668397dfafeb0aab2010ebf309f3bc46ae4d682416e6a547e29506",
  "url": "https://osv.dev/vulnerability/CVE-2026-64539",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Bluetooth: eir: Fix stack OOB write when prepending the Flags AD",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: Bluetooth: eir: Fix stack OOB write when prepending the Flags AD eir_create_adv_data() builds the advertising data into a fixed-size buffer (\"size\", 31 for the legacy path). It may prepend a 3-byte \"Flags\" AD structure (LE_AD_NO_BREDR on an LE-only controller) and then copies the per-instance data without checking that it still fits: memcpy(ptr, adv->adv_data, adv->adv_data_len); tlv_data_max_len() only reserves those 3 bytes when the user-supplied flags carry a managed-flags bit, so an instance added with flags == 0 is accepted with adv_data_len up to the full buffer. At advertise time the flags are still prepended, and the memcpy() writes 3 + adv_data_len bytes into the size-byte buffer: BUG: KASAN: stack-out-of-bounds in eir_create_adv_data (net/bluetooth/eir.c:301) Write of size 31 at addr ffff88800a547bdc by task kworker/u9:0/65 Workqueue: hci0 hci_cmd_sync_work __asan_memcpy (mm/kasan/shadow.c:106) eir_create_adv_data (net/bluetooth/eir.c:301) hci_update_adv_data_sync (net/bluetooth/hci_sync.c:1310) hci_schedule_adv_instance_sync (net/bluetooth/hci_sync.c:1817) hci_cmd_sync_work (net/bluetooth/hci_sync.c:332) This frame has 1 object: [32, 64) 'cp' The \"Flags\" structure is added by the kernel, not requested by userspace, so only prepend it when it fits together with the instance advertising data; when there is no room for both, drop the flags rather than the user-provided data. Reachable by a local user ",
    "evidence": "osv:CVE-2026-64539",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
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            "value": "6.1.178",
            "evidence": "/affected/1/ranges"
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            "value": "6.12.97",
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            "evidence": "/affected/1/ranges"
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          {
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            "evidence": "/affected/1/ranges"
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        "affected_versions": []
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    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-64539",
      "aliases": [
        "CVE-2026-64539"
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      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
        }
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      "modified": "2026-10-28T02:30:50.674249843Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/09301f1fdf2aef8cce34d0c4650c30e7edb1ced9",
        "https://git.kernel.org/stable/c/0f0b6232af56441d0a2dcb173cc4f8d8aab39014",
        "https://git.kernel.org/stable/c/57077eeb586c42f124bc09e018449362223067b3",
        "https://git.kernel.org/stable/c/6f5fb689fdf80bdd143f22a502f9eb1f3c85e286",
        "https://git.kernel.org/stable/c/9174992ee1045c9c96e53eecda64f49dd7e8fbba",
        "https://git.kernel.org/stable/c/f1b4df9c260c51726da2e86e19322825fddeefd0",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64539.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-64539",
        "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/2026/64xxx/CVE-2026-64539.json"
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    "related_cves": [
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        "value": "CVE-2026-64539",
        "evidence": "/id"
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    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 519421,
  "published_at": "2026-07-27T20:10:33.363+00:00"
}