CVE-2026-64433 in Linux
Summary
by MITRE • 07/25/2026
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: MGMT: Fix UAF of hci_conn_params in add_device_complete
add_device_complete() runs from the hci_cmd_sync_work kworker, which holds only hci_req_sync_lock and *not* hci_dev_lock. It calls hci_conn_params_lookup() and then dereferences the returned object (params->flags) without taking hci_dev_lock:
params = hci_conn_params_lookup(hdev, &cp->addr.bdaddr, le_addr_type(cp->addr.type)); ... device_flags_changed(NULL, hdev, &cp->addr.bdaddr, cp->addr.type, hdev->conn_flags, params ? params->flags : 0);
hci_conn_params_lookup() walks hdev->le_conn_params and is documented to require hdev->lock. A concurrent MGMT_OP_REMOVE_DEVICE (remove_device()), which does run under hci_dev_lock, can call hci_conn_params_free() to list_del() and kfree() the very object the lookup returned, so the subsequent params->flags read touches freed memory [0].
Hold hci_dev_lock() across the hci_conn_params_lookup() and the read of params->flags (and the matching event emission) so the lookup result cannot be freed by a concurrent remove_device() before it is used, honouring the locking contract of hci_conn_params_lookup().
[0]: (trailing page/memory-state dump trimmed)
BUG: KASAN: slab-use-after-free in add_device_complete+0x358/0x3d8 net/bluetooth/mgmt.c:7671 Read of size 1 at addr ffff000017ab26c1 by task kworker/u9:8/388
CPU: 1 UID: 0 PID: 388 Comm: kworker/u9:8 Not tainted 7.0.11 #20 PREEMPT Hardware name: linux,dummy-virt (DT) Workqueue: hci0 hci_cmd_sync_work Call trace: show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:499 (C) __dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0xb4/0xd4 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:378 [inline]
print_report+0x118/0x5d8 mm/kasan/report.c:482 kasan_report+0xb0/0xf4 mm/kasan/report.c:595 __asan_report_load1_noabort+0x20/0x2c mm/kasan/report_generic.c:378 add_device_complete+0x358/0x3d8 net/bluetooth/mgmt.c:7671 hci_cmd_sync_work+0x14c/0x240 net/bluetooth/hci_sync.c:334 process_one_work+0x628/0xd38 kernel/workqueue.c:3289 process_scheduled_works kernel/workqueue.c:3372 [inline]
worker_thread+0x7a8/0xac0 kernel/workqueue.c:3453 kthread+0x39c/0x444 kernel/kthread.c:436 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:860
Allocated by task 3401: kasan_save_stack+0x3c/0x64 mm/kasan/common.c:57 kasan_save_track+0x20/0x3c mm/kasan/common.c:78 kasan_save_alloc_info+0x40/0x54 mm/kasan/generic.c:570 poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
__kasan_kmalloc+0xd4/0xd8 mm/kasan/common.c:415 kasan_kmalloc include/linux/kasan.h:263 [inline]
__kmalloc_cache_noprof+0x1b0/0x458 mm/slub.c:5385 kmalloc_noprof include/linux/slab.h:950 [inline]
kzalloc_noprof include/linux/slab.h:1188 [inline]
hci_conn_params_add+0x10c/0x4b0 net/bluetooth/hci_core.c:2279 hci_conn_params_set net/bluetooth/mgmt.c:5162 [inline]
add_device+0x5b4/0xa54 net/bluetooth/mgmt.c:7755 hci_mgmt_cmd net/bluetooth/hci_sock.c:1721 [inline]
hci_sock_sendmsg+0x10b4/0x1dd0 net/bluetooth/hci_sock.c:1841 sock_sendmsg_nosec net/socket.c:727 [inline]
__sock_sendmsg+0xe0/0x128 net/socket.c:742 sock_write_iter+0x250/0x390 net/socket.c:1195 new_sync_write fs/read_write.c:595 [inline]
vfs_write+0x66c/0xab0 fs/read_write.c:688 ksys_write+0x1fc/0x24c fs/read_write.c:740 __do_sys_write fs/read_write.c:751 [inline]
__se_sys_write fs/read_write.c:748 [inline]
__arm64_sys_write+0x70/0xa4 fs/read_write.c:748 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
invoke_syscall+0x84/0x2a8 arch/arm64/kernel/syscall.c:49 el0_svc_common.constprop.0+0xe4/0x294 arch/arm64/kernel/syscall.c:132 do_el0_svc+0x44/0x5c arch/arm64/kernel/syscall.c:151 el0_svc+0x38/0xac arch/arm64/kernel/entry-common.c:724 el0t_64_sync_handler+0xa0/0xe4 arch/arm64/kernel/entry-common.c:743 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596
Freed by task 3740: kasan_save_stack+0x3c/0x64 ---truncated---
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Analysis
by VulDB Data Team • 07/25/2026
The vulnerability described represents a use-after-free condition in the Linux kernel's Bluetooth subsystem, specifically within the management interface handler for HCI (Host Controller Interface) commands. This issue arises from improper locking mechanisms during concurrent access to shared data structures, creating a race condition that can lead to memory corruption and potential exploitation. The flaw is classified as a use-after-free vulnerability under CWE-416, which occurs when a program continues to use a pointer after the memory it points to has been freed.
The core technical issue manifests in the `add_device_complete()` function which executes within the context of a workqueue thread (`hci_cmd_sync_work`) that holds only `hci_req_sync_lock` but not `hci_dev_lock`. This function performs a lookup operation using `hci_conn_params_lookup()` on the device's connection parameters, which is documented to require exclusive access via `hci_dev_lock`. However, the subsequent dereference of the returned structure (`params->flags`) occurs without acquiring this necessary lock, leaving it exposed to concurrent modification by other kernel threads.
The race condition becomes exploitable when a concurrent `MGMT_OP_REMOVE_DEVICE` operation executes under `hci_dev_lock`, calling `hci_conn_params_free()` which performs `list_del()` and `kfree()` on the same memory object that was just retrieved by `hci_conn_params_lookup()`. This creates a scenario where the pointer returned from the lookup becomes invalid immediately after the function call, yet the code attempts to read from it. The kernel's KASAN (Kernel Address Sanitizer) detection confirms this with a slab-use-after-free error, indicating that memory was accessed after being freed.
This vulnerability directly impacts system stability and security, as it can result in kernel crashes through memory corruption or potentially provide an attack surface for privilege escalation if exploited by malicious actors. The flaw demonstrates poor adherence to the locking contracts defined within the kernel's Bluetooth subsystem architecture. According to ATT&CK framework, this represents a technique for privilege escalation through kernel memory corruption (T1068). The fix requires ensuring that `hci_dev_lock` is held across the entire sequence of operations from lookup to dereference, thereby preventing concurrent modification of the connection parameters structure.
The operational impact extends beyond simple system instability, as it affects Bluetooth-enabled devices where management commands are frequently issued. Any application or service that interacts with Bluetooth device management through HCI commands could potentially trigger this race condition. The vulnerability is particularly concerning in embedded systems and IoT devices where Bluetooth functionality is prevalent and system stability is critical. Mitigation efforts must include proper synchronization mechanisms to ensure data consistency across concurrent access paths, and kernel updates should be prioritized to address this issue.
The root cause analysis reveals a fundamental design flaw in the locking strategy within the Bluetooth management interface. The code fails to properly coordinate between different lock contexts, creating a scenario where one thread can free memory that another thread is still accessing. This pattern of improper synchronization represents a common class of vulnerabilities in kernel space programming and underscores the importance of strict adherence to established locking protocols. The fix addresses this by implementing proper locking semantics that maintain data integrity throughout the critical section, ensuring that connection parameters cannot be freed while they are being accessed by other threads in the system.