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GHSA-53R8-C46R-W2FG

Vulnerability from github – Published: 2026-08-15 06:32 – Updated: 2026-08-15 06:32
VLAI
Details

In the Linux kernel, the following vulnerability has been resolved:

Bluetooth: 6lowpan: hold L2CAP conn across debugfs control

get_l2cap_conn() looks up an LE hci_conn under hdev protection, but then drops that protection before reading hcon->l2cap_data and before lowpan_control_write() later dereferences conn->hcon. A disconnect or device close can tear down the same L2CAP connection in that window.

The buggy scenario involves two paths, with each column showing the order within that path:

6LoWPAN control write: HCI disconnect/device close: 1. get_l2cap_conn() finds hcon 1. hci_disconn_cfm() dispatches and hcon->l2cap_data. the L2CAP disconnect callback. 2. get_l2cap_conn() drops hdev 2. l2cap_conn_del() clears protection and returns conn. hcon->l2cap_data and drops the L2CAP connection reference. 3. lowpan_control_write() reads 3. hci_conn_del() removes and drops conn->hcon. the HCI connection.

Take a reference to the L2CAP connection with l2cap_conn_hold_unless_zero() while hdev is still locked, and drop that reference after the debugfs command's last use of conn. This mirrors the existing L2CAP ACL receive-side handoff and keeps the connection dereferenceable after leaving hdev protection. Export the existing helper so the bluetooth_6lowpan module can use the same lifetime primitive.

Validation reproduced this kernel report: BUG: KASAN: slab-use-after-free in lowpan_control_write+0x374/0x520 The buggy address belongs to the object at ffff888111b9d000 which belongs to the cache kmalloc-1k of size 1024 The buggy address is located 0 bytes inside of freed 1024-byte region [ffff888111b9d000, ffff888111b9d400) Read of size 8 Call trace: dump_stack_lvl+0x66/0xa0 print_report+0xce/0x5f0 lowpan_control_write+0x374/0x520 (net/bluetooth/6lowpan.c:1131) srso_alias_return_thunk+0x5/0xfbef5 __virt_addr_valid+0x19f/0x330 kasan_report+0xe0/0x110 __debugfs_file_get+0xf7/0x400 full_proxy_write+0x9e/0xd0 vfs_write+0x1b0/0x810 ksys_write+0xd2/0x170 dnotify_flush+0x32/0x220 do_syscall_64+0x115/0x6a0 (arch/x86/entry/syscall_64.c:87) entry_SYSCALL_64_after_hwframe+0x77/0x7f Allocated by task stack: kasan_save_stack+0x33/0x60 kasan_save_track+0x17/0x60 __kasan_kmalloc+0xaa/0xb0 l2cap_conn_add+0x45/0x520 l2cap_chan_connect+0xac6/0xd90 l2cap_sock_connect+0x216/0x350 __sys_connect+0x101/0x130 __x64_sys_connect+0x40/0x50 do_syscall_64+0x115/0x6a0 (arch/x86/entry/syscall_64.c:87) entry_SYSCALL_64_after_hwframe+0x77/0x7f Freed by task stack: kasan_save_stack+0x33/0x60 kasan_save_track+0x17/0x60 kasan_save_free_info+0x3b/0x60 __kasan_slab_free+0x5f/0x80 kfree+0x313/0x590 hci_conn_hash_flush+0xc0/0x140 hci_dev_close_sync+0x41a/0xb00 hci_dev_close+0x12f/0x160 hci_sock_ioctl+0x157/0x570 sock_do_ioctl+0xf7/0x210 sock_ioctl+0x32f/0x490 __x64_sys_ioctl+0xc7/0x110 do_syscall_64+0x115/0x6a0 (arch/x86/entry/syscall_64.c:87) entry_SYSCALL_64_after_hwframe+0x77/0x7f kasan_record_aux_stack+0xa7/0xc0 insert_work+0x32/0x100 __queue_work+0x262/0xa60 queue_work_on+0xad/0xb0 l2cap_connect_cfm+0x4ef/0x670 hci_le_remote_feat_complete_evt+0x247/0x430 hci_event_packet+0x360/0x6f0 hci_rx_work+0x2ae/0x7a0 process_one_work+0x4fd/0xbc0 worker_thread+0x2d8/0x570 kthread+0x1ad/0x1f0 ret_from_fork+0x3c9/0x540 ret_from_fork_asm+0x1a/0x30

Show details on source website

{
  "affected": [],
  "aliases": [
    "CVE-2026-72336"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-08-15T06:22:06Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nBluetooth: 6lowpan: hold L2CAP conn across debugfs control\n\nget_l2cap_conn() looks up an LE hci_conn under hdev protection, but\nthen drops that protection before reading hcon-\u003el2cap_data and before\nlowpan_control_write() later dereferences conn-\u003ehcon.  A disconnect or\ndevice close can tear down the same L2CAP connection in that window.\n\nThe buggy scenario involves two paths, with each column showing the order\nwithin that path:\n\n6LoWPAN control write:              HCI disconnect/device close:\n  1. get_l2cap_conn() finds hcon      1. hci_disconn_cfm() dispatches\n     and hcon-\u003el2cap_data.               the L2CAP disconnect callback.\n  2. get_l2cap_conn() drops hdev      2. l2cap_conn_del() clears\n     protection and returns conn.        hcon-\u003el2cap_data and drops the\n                                         L2CAP connection reference.\n  3. lowpan_control_write() reads     3. hci_conn_del() removes and drops\n     conn-\u003ehcon.                         the HCI connection.\n\nTake a reference to the L2CAP connection with\nl2cap_conn_hold_unless_zero() while hdev is still locked, and drop that\nreference after the debugfs command\u0027s last use of conn.  This mirrors the\nexisting L2CAP ACL receive-side handoff and keeps the connection\ndereferenceable after leaving hdev protection.  Export the existing helper\nso the bluetooth_6lowpan module can use the same lifetime primitive.\n\nValidation reproduced this kernel report:\nBUG: KASAN: slab-use-after-free in lowpan_control_write+0x374/0x520\nThe buggy address belongs to the object at ffff888111b9d000 which belongs\nto the cache kmalloc-1k of size 1024\nThe buggy address is located 0 bytes inside of freed 1024-byte region\n[ffff888111b9d000, ffff888111b9d400)\nRead of size 8\nCall trace:\n  dump_stack_lvl+0x66/0xa0\n  print_report+0xce/0x5f0\n  lowpan_control_write+0x374/0x520 (net/bluetooth/6lowpan.c:1131)\n  srso_alias_return_thunk+0x5/0xfbef5\n  __virt_addr_valid+0x19f/0x330\n  kasan_report+0xe0/0x110\n  __debugfs_file_get+0xf7/0x400\n  full_proxy_write+0x9e/0xd0\n  vfs_write+0x1b0/0x810\n  ksys_write+0xd2/0x170\n  dnotify_flush+0x32/0x220\n  do_syscall_64+0x115/0x6a0 (arch/x86/entry/syscall_64.c:87)\n  entry_SYSCALL_64_after_hwframe+0x77/0x7f\nAllocated by task stack:\n  kasan_save_stack+0x33/0x60\n  kasan_save_track+0x17/0x60\n  __kasan_kmalloc+0xaa/0xb0\n  l2cap_conn_add+0x45/0x520\n  l2cap_chan_connect+0xac6/0xd90\n  l2cap_sock_connect+0x216/0x350\n  __sys_connect+0x101/0x130\n  __x64_sys_connect+0x40/0x50\n  do_syscall_64+0x115/0x6a0 (arch/x86/entry/syscall_64.c:87)\n  entry_SYSCALL_64_after_hwframe+0x77/0x7f\nFreed by task stack:\n  kasan_save_stack+0x33/0x60\n  kasan_save_track+0x17/0x60\n  kasan_save_free_info+0x3b/0x60\n  __kasan_slab_free+0x5f/0x80\n  kfree+0x313/0x590\n  hci_conn_hash_flush+0xc0/0x140\n  hci_dev_close_sync+0x41a/0xb00\n  hci_dev_close+0x12f/0x160\n  hci_sock_ioctl+0x157/0x570\n  sock_do_ioctl+0xf7/0x210\n  sock_ioctl+0x32f/0x490\n  __x64_sys_ioctl+0xc7/0x110\n  do_syscall_64+0x115/0x6a0 (arch/x86/entry/syscall_64.c:87)\n  entry_SYSCALL_64_after_hwframe+0x77/0x7f\n  kasan_record_aux_stack+0xa7/0xc0\n  insert_work+0x32/0x100\n  __queue_work+0x262/0xa60\n  queue_work_on+0xad/0xb0\n  l2cap_connect_cfm+0x4ef/0x670\n  hci_le_remote_feat_complete_evt+0x247/0x430\n  hci_event_packet+0x360/0x6f0\n  hci_rx_work+0x2ae/0x7a0\n  process_one_work+0x4fd/0xbc0\n  worker_thread+0x2d8/0x570\n  kthread+0x1ad/0x1f0\n  ret_from_fork+0x3c9/0x540\n  ret_from_fork_asm+0x1a/0x30",
  "id": "GHSA-53r8-c46r-w2fg",
  "modified": "2026-08-15T06:32:20Z",
  "published": "2026-08-15T06:32:20Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-72336"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/23a83bac3356e7b211bcdcf581a31f7b536a2c24"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/32c48c7f6cc8c7888e46a8c81622154ccafda5d2"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/518aa9505fa10ea5662349e5d2efd8c9e32a820b"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/ba1f1ef6522e63aa5dd29805b4390ea2ccadf05e"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/d2a8dc1f619c9e0e4126bee795c39ebddd2ec8ff"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}



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