--- id: CVE-2026-64434 title: 'Bluetooth: L2CAP: Fix UAF in channel timeout by holding conn ref' summary: |- In the Linux kernel, the following vulnerability has been resolved: Bluetooth: L2CAP: Fix UAF in channel timeout by holding conn ref l2cap_chan_timeout() runs asynchronously and accesses chan->conn. If the connection is torn down while… severity: high cvss: 8.8 cvssVector: 'CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H' cvssSource: cna vendor: Linux product: Linux affected: - >- Linux >= 3634cbdc2eb414b69ffa752ddbe5e0458518e321 < 8f90405a4a6f1f1880dc07996b47bf57c712bd8a - >- Linux >= e1c100e2d61bd8c718b7d91fe3e050780a9bf72d < 32d783cafb46ff3ca58e6f9fd62c9c5f35eaf26b - >- Linux >= deb8493a8fa599f6c95e2465b12bfdfb7f94a1d9 < 8922c7940bae9ce4b1736dddb6362370793835c2 - >- Linux >= 89dec92041717b027216e110599e4f6d6c921b79 < 91047a4396a8b1857a6f712a90cf33ec0012b189 - >- Linux >= 50dfec218808b148ab4247b1858031b7a32015c5 < 0b0e2bf39cf99e458d991b9df253727e036a7d7d - >- Linux >= 859d3ace791ed878ae9ba5522c7844d960da8f88 < d3b739db5dc6f688a60d56da872fabaf65246032 - >- Linux >= 8c8e620467a7b51562dbcefbd1f09f288d7d710d < 50c38d9f42a529691e4e67ea9cedf4f0bfc8d277 - >- Linux >= 8c8e620467a7b51562dbcefbd1f09f288d7d710d < b66774b48dd98f07254951f74ea6f513efe7ff8b - Linux 7555fd885a0603f50e49a655850a1f2bd8a25398 - Linux >= 5.10.259 < 5.10.265 - Linux >= 5.15.210 < 5.15.216 - Linux >= 6.1.176 < 6.1.183 - Linux >= 6.6.143 < 6.6.145 - Linux >= 6.12.93 < 6.12.97 - Linux >= 6.18.35 < 6.18.39 - Linux >= 7.0.12 < 7.1 - Linux 7.1 ssvc: exploitation: none automatable: 'no' technicalImpact: total timestamp: '2026-10-16T15:40:36.220743Z' published: '2026-07-25' updated: '2026-10-16' sourceUpdated: '2026-10-16T15:42:35.391Z' source: CVEORG sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-64434' references: - url: 'https://git.kernel.org/stable/c/8f90405a4a6f1f1880dc07996b47bf57c712bd8a' - url: 'https://git.kernel.org/stable/c/32d783cafb46ff3ca58e6f9fd62c9c5f35eaf26b' - url: 'https://git.kernel.org/stable/c/8922c7940bae9ce4b1736dddb6362370793835c2' - url: 'https://git.kernel.org/stable/c/91047a4396a8b1857a6f712a90cf33ec0012b189' - url: 'https://git.kernel.org/stable/c/0b0e2bf39cf99e458d991b9df253727e036a7d7d' - url: 'https://git.kernel.org/stable/c/d3b739db5dc6f688a60d56da872fabaf65246032' - url: 'https://git.kernel.org/stable/c/50c38d9f42a529691e4e67ea9cedf4f0bfc8d277' - url: 'https://git.kernel.org/stable/c/b66774b48dd98f07254951f74ea6f513efe7ff8b' tags: - cve.org epss: 0.00255 epssPercentile: 0.15954 ingestedAt: '2026-10-16T17:24:46.819Z' --- ## Overview In the Linux kernel, the following vulnerability has been resolved: Bluetooth: L2CAP: Fix UAF in channel timeout by holding conn ref l2cap_chan_timeout() runs asynchronously and accesses chan->conn. If the connection is torn down while the timer is running or pending, chan->conn can be freed, leading to a use-after-free when the timer worker attempts to lock conn->lock: | BUG: KASAN: slab-use-after-free in instrument_atomic_read_write include/linux/instrumented.h:112 [inline] | BUG: KASAN: slab-use-after-free in atomic_long_try_cmpxchg_acquire include/linux/atomic/atomic-instrumented.h:4456 [inline] | BUG: KASAN: slab-use-after-free in __mutex_trylock_fast kernel/locking/mutex.c:161 [inline] | BUG: KASAN: slab-use-after-free in mutex_lock+0x4f/0xa0 kernel/locking/mutex.c:318 | Write of size 8 at addr ffff8881298d9550 by task kworker/2:1/83 | | CPU: 2 UID: 0 PID: 83 Comm: kworker/2:1 Not tainted 7.1.0-rc6-next-20260601-dirty #6 PREEMPT(full) | Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-debian-1.17.0-1 04/01/2014 | Workqueue: events l2cap_chan_timeout | Call Trace: | | instrument_atomic_read_write include/linux/instrumented.h:112 [inline] | atomic_long_try_cmpxchg_acquire include/linux/atomic/atomic-instrumented.h:4456 [inline] | __mutex_trylock_fast kernel/locking/mutex.c:161 [inline] | mutex_lock+0x4f/0xa0 kernel/locking/mutex.c:318 | l2cap_chan_timeout+0x5d/0x1b0 net/bluetooth/l2cap_core.c:422 | process_one_work kernel/workqueue.c:3326 [inline] | process_scheduled_works+0x7c8/0xfb0 kernel/workqueue.c:3409 | worker_thread+0x8a9/0xcf0 kernel/workqueue.c:3490 | kthread+0x346/0x430 kernel/kthread.c:436 | ret_from_fork+0x1a3/0x470 arch/x86/kernel/process.c:158 | ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 | | | Allocated by task 320: | l2cap_conn_add+0xa7/0x820 net/bluetooth/l2cap_core.c:7075 | l2cap_connect_cfm+0xdb/0xd70 net/bluetooth/l2cap_core.c:7452 | hci_connect_cfm include/net/bluetooth/hci_core.h:2139 [inline] | hci_remote_features_evt+0x52f/0x9f0 net/bluetooth/hci_event.c:3760 | hci_event_func net/bluetooth/hci_event.c:7796 [inline] | hci_event_packet+0x561/0xa70 net/bluetooth/hci_event.c:7847 | hci_rx_work+0x370/0x890 net/bluetooth/hci_core.c:4040 | process_one_work kernel/workqueue.c:3326 [inline] | process_scheduled_works+0x7c8/0xfb0 kernel/workqueue.c:3409 | worker_thread+0x8a9/0xcf0 kernel/workqueue.c:3490 | kthread+0x346/0x430 kernel/kthread.c:436 | ret_from_fork+0x1a3/0x470 arch/x86/kernel/process.c:158 | ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 | | Freed by task 322: | hci_disconn_cfm include/net/bluetooth/hci_core.h:2154 [inline] | hci_conn_hash_flush+0x101/0x1f0 net/bluetooth/hci_conn.c:2736 | hci_dev_close_sync+0x889/0xde0 net/bluetooth/hci_sync.c:5405 | hci_dev_do_close net/bluetooth/hci_core.c:502 [inline] | hci_unregister_dev+0x1f7/0x370 net/bluetooth/hci_core.c:2679 | vhci_release+0x12a/0x180 drivers/bluetooth/hci_vhci.c:690 | __fput+0x369/0x890 fs/file_table.c:510 | task_work_run+0x160/0x1d0 kernel/task_work.c:233 | get_signal+0xf5b/0x1120 kernel/signal.c:2810 | arch_do_signal_or_restart+0x4d/0x600 arch/x86/kernel/signal.c:337 | __exit_to_user_mode_loop kernel/entry/common.c:64 [inline] | exit_to_user_mode_loop+0x85/0x510 kernel/entry/common.c:98 | do_syscall_64+0x263/0x3d0 arch/x86/entry/syscall_64.c:100 | entry_SYSCALL_64_after_hwframe+0x77/0x7f | | The buggy address belongs to the object at ffff8881298d9400 | which belongs to the cache kmalloc-512 of size 512 | The buggy address is located 336 bytes inside of | freed 512-byte region [ffff8881298d9400, ffff8881298d9600) Fix it by having chan->conn hold a reference to l2cap_conn (via l2cap_conn_get) when the channel is added to the connection, and releasing it in the channel destructor. This ensures the l2cap_conn remains alive as long as the channel exists. A new FLAG_DEL channel flag is introduced to indicate that the ch ---truncated--- ## Affected - `Linux >= 3634cbdc2eb414b69ffa752ddbe5e0458518e321 < 8f90405a4a6f1f1880dc07996b47bf57c712bd8a` - `Linux >= e1c100e2d61bd8c718b7d91fe3e050780a9bf72d < 32d783cafb46ff3ca58e6f9fd62c9c5f35eaf26b` - `Linux >= deb8493a8fa599f6c95e2465b12bfdfb7f94a1d9 < 8922c7940bae9ce4b1736dddb6362370793835c2` - `Linux >= 89dec92041717b027216e110599e4f6d6c921b79 < 91047a4396a8b1857a6f712a90cf33ec0012b189` - `Linux >= 50dfec218808b148ab4247b1858031b7a32015c5 < 0b0e2bf39cf99e458d991b9df253727e036a7d7d` - `Linux >= 859d3ace791ed878ae9ba5522c7844d960da8f88 < d3b739db5dc6f688a60d56da872fabaf65246032` - `Linux >= 8c8e620467a7b51562dbcefbd1f09f288d7d710d < 50c38d9f42a529691e4e67ea9cedf4f0bfc8d277` - `Linux >= 8c8e620467a7b51562dbcefbd1f09f288d7d710d < b66774b48dd98f07254951f74ea6f513efe7ff8b` - `Linux 7555fd885a0603f50e49a655850a1f2bd8a25398` - `Linux >= 5.10.259 < 5.10.265` - `Linux >= 5.15.210 < 5.15.216` - `Linux >= 6.1.176 < 6.1.183` - `Linux >= 6.6.143 < 6.6.145` - `Linux >= 6.12.93 < 6.12.97` - `Linux >= 6.18.35 < 6.18.39` - `Linux >= 7.0.12 < 7.1` - `Linux 7.1` ## Remediation Refer to the linked advisories for vendor-supplied fixes and affected version ranges.