CVE-2026-72336
Full vulnerability record from the local CVENow database.
Description
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
View original CVE JSON
{
"id": "CVE-2026-72336",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"published": "2026-08-15T06:22:06.817",
"lastModified": "2026-10-30T13:19:49.630",
"vulnStatus": "Received",
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "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->l2cap_data and before\nlowpan_control_write() later dereferences conn->hcon. 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->l2cap_data. the L2CAP disconnect callback.\n 2. get_l2cap_conn() drops hdev 2. l2cap_conn_del() clears\n protection and returns conn. hcon->l2cap_data and drops the\n L2CAP connection reference.\n 3. lowpan_control_write() reads 3. hci_conn_del() removes and drops\n conn->hcon. 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's 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"
}
],
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
"vendor": "Linux",
"product": "Linux",
"defaultStatus": "unaffected",
"programFiles": [
"net/bluetooth/6lowpan.c",
"net/bluetooth/l2cap_core.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"versions": [
{
"version": "6b8d4a6a03144c5996f98db7f8256267b0d72a3a",
"lessThan": "1df008a0770843caaeb7148705fc104bfb266630",
"versionType": "git",
"status": "affected"
},
{
"version": "6b8d4a6a03144c5996f98db7f8256267b0d72a3a",
"lessThan": "ba1f1ef6522e63aa5dd29805b4390ea2ccadf05e",
"versionType": "git",
"status": "affected"
},
{
"version": "6b8d4a6a03144c5996f98db7f8256267b0d72a3a",
"lessThan": "d2a8dc1f619c9e0e4126bee795c39ebddd2ec8ff",
"versionType": "git",
"status": "affected"
},
{
"version": "6b8d4a6a03144c5996f98db7f8256267b0d72a3a",
"lessThan": "23a83bac3356e7b211bcdcf581a31f7b536a2c24",
"versionType": "git",
"status": "affected"
},
{
"version": "6b8d4a6a03144c5996f98db7f8256267b0d72a3a",
"lessThan": "32c48c7f6cc8c7888e46a8c81622154ccafda5d2",
"versionType": "git",
"status": "affected"
},
{
"version": "6b8d4a6a03144c5996f98db7f8256267b0d72a3a",
"lessThan": "518aa9505fa10ea5662349e5d2efd8c9e32a820b",
"versionType": "git",
"status": "affected"
}
]
},
{
"vendor": "Linux",
"product": "Linux",
"defaultStatus": "affected",
"programFiles": [
"net/bluetooth/6lowpan.c",
"net/bluetooth/l2cap_core.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"versions": [
{
"version": "3.17",
"status": "affected"
},
{
"version": "0",
"lessThan": "3.17",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.1.191",
"lessThanOrEqual": "6.1.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.6.145",
"lessThanOrEqual": "6.6.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.12.97",
"lessThanOrEqual": "6.12.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.18.40",
"lessThanOrEqual": "6.18.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "7.1.5",
"lessThanOrEqual": "7.1.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "7.2",
"lessThanOrEqual": "*",
"versionType": "original_commit_for_fix",
"status": "unaffected"
}
]
}
]
}
],
"metrics": {},
"references": [
{
"url": "https://git.kernel.org/stable/c/1df008a0770843caaeb7148705fc104bfb266630",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/23a83bac3356e7b211bcdcf581a31f7b536a2c24",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/32c48c7f6cc8c7888e46a8c81622154ccafda5d2",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/518aa9505fa10ea5662349e5d2efd8c9e32a820b",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/ba1f1ef6522e63aa5dd29805b4390ea2ccadf05e",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/d2a8dc1f619c9e0e4126bee795c39ebddd2ec8ff",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
]
}