Bluetooth: hci_sync: fix stack buffer overflow in hci_le_big_create_sync_CVE-2026-31772

{
    "lastseen": "",
    "description": "In the Linux kernel, the following vulnerability has been resolved:\n\nBluetooth: hci_sync: fix stack buffer overflow in hci_le_big_create_sync\n\nhci_le_big_create_sync() uses DEFINE_FLEX to allocate a\nstruct hci_cp_le_big_create_sync on the stack with room for 0x11 (17)\nBIS entries.  However, conn->num_bis can hold up to HCI_MAX_ISO_BIS (31)\nentries \u2014 validated against ISO_MAX_NUM_BIS (0x1f) in the caller\nhci_conn_big_create_sync().  When conn->num_bis is between 18 and 31,\nthe memcpy that copies conn->bis into cp->bis writes up to 14 bytes\npast the stack buffer, corrupting adjacent stack memory.\n\nThis is trivially reproducible: binding an ISO socket with\nbc_num_bis = ISO_MAX_NUM_BIS (31) and calling listen() will\neventually trigger hci_le_big_create_sync() from the HCI command\nsync worker, causing a KASAN-detectable stack-out-of-bounds write:\n\n  BUG: KASAN: stack-out-of-bounds in hci_le_big_create_sync+0x256/0x3b0\n  Write of size 31 at addr ffffc90000487b48 by task kworker/u9:0/71\n\nFix this by changing the DEFINE_FLEX count from the incorrect 0x11 to\nHCI_MAX_ISO_BIS, which matches the maximum number of BIS entries that\nconn->bis can actually carry.",
    "published": "2026-05-01T14:15:00.582Z",
    "modified": "2026-05-03T05:45:52.849Z",
    "type": "cve",
    "title": "Bluetooth: hci_sync: fix stack buffer overflow in hci_le_big_create_sync",
    "source": "Linux",
    "references": "https://git.kernel.org/stable/c/f5d446624345d309e7a4a1b27ea9f028d6a8c5d9\nhttps://git.kernel.org/stable/c/aba0aea354015794e8312dd7efe726967e58aefe\nhttps://git.kernel.org/stable/c/eaf32002ca7b1ba51c9f140991fd9febe6de79f0\nhttps://git.kernel.org/stable/c/bc39a094730ce062fa034a529c93147c096cb488",
    "id": "CVE-2026-31772",
    "bulletinFamily": "",
    "cwe": null,
    "cvelist": null,
    "sourceData": "Linux Linux 91d19383b7ed035e22165ae5c836e50bb9f95fbe\nLinux Linux 42ecf1947135110ea08abeaca39741636f9a2285\nLinux Linux 42ecf1947135110ea08abeaca39741636f9a2285\nLinux Linux 42ecf1947135110ea08abeaca39741636f9a2285\nLinux Linux 8958e1cee4e2eac1a5b825caa4dd96ce9ed975dd\nLinux Linux 6.13",
    "sourceHref": "",
    "cvss": {
        "score": 7.8,
        "severity": "HIGH",
        "vector": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
        "version": "3.1"
    },
    "cvss2": [],
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        "baseScore": 0,
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        "attackComplexity": "",
        "privilegesRequired": "",
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        "scope": "",
        "confidentialityImpact": "",
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        "availabilityImpact": "",
        "cvssV3": {
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            "baseScore": 0,
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    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "Linux",
    "version": "91d19383b7ed035e22165ae5c836e50bb9f95fbe",
    "vendor": "Linux",
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    "ai_score": 0
}