{"id":"CVE-2026-72336","state":"PUBLISHED","title":"Bluetooth: 6lowpan: hold L2CAP conn across debugfs control","description":"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","publishedAt":"2026-08-15T05:55:44.487Z","updatedAt":"2026-10-30T12:29:06.091Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"6b8d4a6a03144c5996f98db7f8256267b0d72a3a","status":"affected","lessThan":"1df008a0770843caaeb7148705fc104bfb266630","versionType":"git"},{"version":"6b8d4a6a03144c5996f98db7f8256267b0d72a3a","status":"affected","lessThan":"ba1f1ef6522e63aa5dd29805b4390ea2ccadf05e","versionType":"git"},{"version":"6b8d4a6a03144c5996f98db7f8256267b0d72a3a","status":"affected","lessThan":"d2a8dc1f619c9e0e4126bee795c39ebddd2ec8ff","versionType":"git"},{"version":"6b8d4a6a03144c5996f98db7f8256267b0d72a3a","status":"affected","lessThan":"23a83bac3356e7b211bcdcf581a31f7b536a2c24","versionType":"git"},{"version":"6b8d4a6a03144c5996f98db7f8256267b0d72a3a","status":"affected","lessThan":"32c48c7f6cc8c7888e46a8c81622154ccafda5d2","versionType":"git"},{"version":"6b8d4a6a03144c5996f98db7f8256267b0d72a3a","status":"affected","lessThan":"518aa9505fa10ea5662349e5d2efd8c9e32a820b","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/bluetooth/6lowpan.c","net/bluetooth/l2cap_core.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"3.17","status":"affected"},{"version":"0","status":"unaffected","lessThan":"3.17","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.145","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.97","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.40","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.5","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/bluetooth/6lowpan.c","net/bluetooth/l2cap_core.c"]}],"references":["https://git.kernel.org/stable/c/1df008a0770843caaeb7148705fc104bfb266630","https://git.kernel.org/stable/c/ba1f1ef6522e63aa5dd29805b4390ea2ccadf05e","https://git.kernel.org/stable/c/d2a8dc1f619c9e0e4126bee795c39ebddd2ec8ff","https://git.kernel.org/stable/c/23a83bac3356e7b211bcdcf581a31f7b536a2c24","https://git.kernel.org/stable/c/32c48c7f6cc8c7888e46a8c81622154ccafda5d2","https://git.kernel.org/stable/c/518aa9505fa10ea5662349e5d2efd8c9e32a820b"],"weaknesses":[],"ingestedAt":"2026-10-30T12:48:04.825Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/72xxx/CVE-2026-72336.json","commit":"1f312381e38164a43607eebab851b151dd16861e","baselineCommit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-72336","state":"PUBLISHED","datePublished":"2026-08-15T05:55:44.487Z","dateUpdated":"2026-10-30T12:29:06.091Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-08-09T03:40:39.920Z"},"containers":{"cna":{"title":"Bluetooth: 6lowpan: hold L2CAP conn across debugfs control","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":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"6b8d4a6a03144c5996f98db7f8256267b0d72a3a","status":"affected","lessThan":"1df008a0770843caaeb7148705fc104bfb266630","versionType":"git"},{"version":"6b8d4a6a03144c5996f98db7f8256267b0d72a3a","status":"affected","lessThan":"ba1f1ef6522e63aa5dd29805b4390ea2ccadf05e","versionType":"git"},{"version":"6b8d4a6a03144c5996f98db7f8256267b0d72a3a","status":"affected","lessThan":"d2a8dc1f619c9e0e4126bee795c39ebddd2ec8ff","versionType":"git"},{"version":"6b8d4a6a03144c5996f98db7f8256267b0d72a3a","status":"affected","lessThan":"23a83bac3356e7b211bcdcf581a31f7b536a2c24","versionType":"git"},{"version":"6b8d4a6a03144c5996f98db7f8256267b0d72a3a","status":"affected","lessThan":"32c48c7f6cc8c7888e46a8c81622154ccafda5d2","versionType":"git"},{"version":"6b8d4a6a03144c5996f98db7f8256267b0d72a3a","status":"affected","lessThan":"518aa9505fa10ea5662349e5d2efd8c9e32a820b","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/bluetooth/6lowpan.c","net/bluetooth/l2cap_core.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"3.17","status":"affected"},{"version":"0","status":"unaffected","lessThan":"3.17","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.145","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.97","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.40","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.5","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/bluetooth/6lowpan.c","net/bluetooth/l2cap_core.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/1df008a0770843caaeb7148705fc104bfb266630"},{"url":"https://git.kernel.org/stable/c/ba1f1ef6522e63aa5dd29805b4390ea2ccadf05e"},{"url":"https://git.kernel.org/stable/c/d2a8dc1f619c9e0e4126bee795c39ebddd2ec8ff"},{"url":"https://git.kernel.org/stable/c/23a83bac3356e7b211bcdcf581a31f7b536a2c24"},{"url":"https://git.kernel.org/stable/c/32c48c7f6cc8c7888e46a8c81622154ccafda5d2"},{"url":"https://git.kernel.org/stable/c/518aa9505fa10ea5662349e5d2efd8c9e32a820b"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-30T12:29:06.091Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.17","versionEndExcluding":"6.1.191"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.17","versionEndExcluding":"6.6.145"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.17","versionEndExcluding":"6.12.97"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.17","versionEndExcluding":"6.18.40"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.17","versionEndExcluding":"7.1.5"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.17","versionEndExcluding":"7.2"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}