{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2026-31772",
  "modified": "2026-10-09T11:39:44Z",
  "upstream": [
    "CVE-2026-31772"
  ],
  "published": "2026-05-01T14:17:31Z",
  "summary": "Bluetooth: hci_sync: fix stack buffer overflow in hci_le_big_create_sync",
  "details": "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.",
  "severity": [
    {
      "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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  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-31772"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/f5d446624345d309e7a4a1b27ea9f028d6a8c5d9"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/aba0aea354015794e8312dd7efe726967e58aefe"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/eaf32002ca7b1ba51c9f140991fd9febe6de79f0"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/bc39a094730ce062fa034a529c93147c096cb488"
    }
  ],
  "database_specific": {
    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-08-05T13:16:28Z",
    "severity": {
      "source": "kernel CNA",
      "cvss_v3_score": 7.8,
      "cvss_v3_severity": "High",
      "scenario": "AV:L - The overflow is reached through locally created AF_BLUETOOTH ISO sockets via bind/listen or deferred receive; the Bluetooth BIG Info event only completes a userspace-initiated ISO sync path.\nAC:L - An attacker can choose a valid bc_num_bis value from 18 to 31 and valid BIS indexes, with no race or hard-to-control memory condition required.\nPR:L - Creating, binding, and listening on BTPROTO_ISO sockets does not require CAP_NET_ADMIN or other elevated capabilities, but it does require local code execution as an unprivileged user.\nUI:N - The attacker can trigger the vulnerable socket operations and resulting HCI sync worker path without any victim action.\nS:U - The corruption occurs within the kernel and affects the same operating-system security authority; ordinary kernel privilege escalation remains scope unchanged.\nC:H - This is kernel stack memory corruption from an out-of-bounds write, which can plausibly be leveraged to disclose sensitive kernel memory when exploited.\nI:H - The bug is a controlled out-of-bounds write past a stack buffer in kernel context, making high-integrity impact defensible.\nA:H - The issue is KASAN-reproducible as a stack out-of-bounds write in a kernel worker and can crash or destabilize the kernel."
    }
  }
}