CVE-2025-39982 Bluetooth: hci_event: Fix UAF in hci_acl_create_conn_sync

What is CVE-2025-39982?

CVE-2025-39982 is a high-severity use after free vulnerability in Linux, published on 15 Oct 2025. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

In the Linux kernel, the following vulnerability has been resolved:

Bluetooth: hci_event: Fix UAF in hci_acl_create_conn_sync

This fixes the following UFA in hci_acl_create_conn_sync where a connection still pending is command submission (conn->state == BT_OPEN) maybe freed, also since this also can happen with the likes of hci_le_create_conn_sync fix it as well:

BUG: KASAN: slab-use-after-free in hci_acl_create_conn_sync+0x5ef/0x790 net/bluetooth/hci_sync.c:6861 Write of size 2 at addr ffff88805ffcc038 by task kworker/u11:2/9541

CPU: 1 UID: 0 PID: 9541 Comm: kworker/u11:2 Not tainted 6.16.0-rc7 #3 PREEMPT(full) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014 Workqueue: hci3 hci_cmd_sync_work Call Trace: <TASK> dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:378 [inline] print_report+0xca/0x230 mm/kasan/report.c:480 kasan_report+0x118/0x150 mm/kasan/report.c:593 hci_acl_create_conn_sync+0x5ef/0x790 net/bluetooth/hci_sync.c:6861 hci_cmd_sync_work+0x210/0x3a0 net/bluetooth/hci_sync.c:332 process_one_work kernel/workqueue.c:3238 [inline] process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3321 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3402 kthread+0x70e/0x8a0 kernel/kthread.c:464 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 home/kwqcheii/source/fuzzing/kernel/kasan/linux-6.16-rc7/arch/x86/entry/entry_64.S:245 </TASK>

Allocated by task 123736: kasan_save_stack mm/kasan/common.c:47 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:68 poison_kmalloc_redzone mm/kasan/common.c:377 [inline] __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:394 kasan_kmalloc include/linux/kasan.h:260 [inline] __kmalloc_cache_noprof+0x230/0x3d0 mm/slub.c:4359 kmalloc_noprof include/linux/slab.h:905 [inline] kzalloc_noprof include/linux/slab.h:1039 [inline] __hci_conn_add+0x233/0x1b30 net/bluetooth/hci_conn.c:939 hci_conn_add_unset net/bluetooth/hci_conn.c:1051 [inline] hci_connect_acl+0x16c/0x4e0 net/bluetooth/hci_conn.c:1634 pair_device+0x418/0xa70 net/bluetooth/mgmt.c:3556 hci_mgmt_cmd+0x9c9/0xef0 net/bluetooth/hci_sock.c:1719 hci_sock_sendmsg+0x6ca/0xef0 net/bluetooth/hci_sock.c:1839 sock_sendmsg_nosec net/socket.c:712 [inline] __sock_sendmsg+0x219/0x270 net/socket.c:727 sock_write_iter+0x258/0x330 net/socket.c:1131 new_sync_write fs/read_write.c:593 [inline] vfs_write+0x54b/0xa90 fs/read_write.c:686 ksys_write+0x145/0x250 fs/read_write.c:738 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 103680: kasan_save_stack mm/kasan/common.c:47 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:68 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:576 poison_slab_object mm/kasan/common.c:247 [inline] __kasan_slab_free+0x62/0x70 mm/kasan/common.c:264 kasan_slab_free include/linux/kasan.h:233 [inline] slab_free_hook mm/slub.c:2381 [inline] slab_free mm/slub.c:4643 [inline] kfree+0x18e/0x440 mm/slub.c:4842 device_release+0x9c/0x1c0 kobject_cleanup lib/kobject.c:689 [inline] kobject_release lib/kobject.c:720 [inline] kref_put include/linux/kref.h:65 [inline] kobject_put+0x22b/0x480 lib/kobject.c:737 hci_conn_cleanup net/bluetooth/hci_conn.c:175 [inline] hci_conn_del+0x8ff/0xcb0 net/bluetooth/hci_conn.c:1173 hci_conn_complete_evt+0x3c7/0x1040 net/bluetooth/hci_event.c:3199 hci_event_func net/bluetooth/hci_event.c:7477 [inline] hci_event_packet+0x7e0/0x1200 net/bluetooth/hci_event.c:7531 hci_rx_work+0x46a/0xe80 net/bluetooth/hci_core.c:4070 process_one_work kernel/workqueue.c:3238 [inline] process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3321 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3402 kthread+0x70e/0x8a0 kernel/kthread.c:464 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 home/kwqcheii/sour ---truncated---

Which versions are affected by CVE-2025-39982?

How do I fix CVE-2025-39982?

Apply the vendor's patch.

Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.

Is CVE-2025-39982 being exploited?

There is no known exploitation of CVE-2025-39982 in the wild and no public exploit code.

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as AZL-68522, BELL-CVE-2025-39982, DEBIAN-CVE-2025-39982, GHSA-jm87-4mhh-83rp, ROOT-OS-DEBIAN-12-CVE-2025-39982, ROOT-OS-DEBIAN-13-CVE-2025-39982 and 2 more.