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Linux Kernel CVE-2025-39983

HIGH
2025-10-15 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Information Disclosure Linux Red Hat Suse
8.8
CVSS 3.1 · Vendor: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
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Severity by source

Vendor (416baaa9-dc9f-4396-8d5f-8c081fb06d67) PRIMARY
8.8 HIGH
AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
vuln.today AI
6.4 MEDIUM

Bluetooth-range vector (AV:A); race condition makes reliable triggering hard (AC:H); proximity-only, no auth (PR:N/UI:N); most reliable impact is kernel crash (A:H) with limited memory read (C:L/I:L).

3.1 AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H
4.0 AV:A/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:H/SC:N/SI:N/SA:N
SUSE
5.5 MEDIUM
AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Red Hat
6.4 MEDIUM
qualitative

Primary rating from Vendor (416baaa9-dc9f-4396-8d5f-8c081fb06d67).

CVSS VectorVendor: 416baaa9-dc9f-4396-8d5f-8c081fb06d67

Attack Vector
Adjacent
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

Lifecycle Timeline

2
Analysis Generated
Jul 30, 2026 - 08:06 vuln.today
CVE Published
Oct 15, 2025 - 08:15 cve.org
HIGH 8.8

DescriptionCVE.org

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

Bluetooth: hci_event: Fix UAF in hci_conn_tx_dequeue

This fixes the following UAF caused by not properly locking hdev when processing HCI_EV_NUM_COMP_PKTS:

BUG: KASAN: slab-use-after-free in hci_conn_tx_dequeue+0x1be/0x220 net/bluetooth/hci_conn.c:3036 Read of size 4 at addr ffff8880740f0940 by task kworker/u11:0/54

CPU: 1 UID: 0 PID: 54 Comm: kworker/u11:0 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: hci1 hci_rx_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_conn_tx_dequeue+0x1be/0x220 net/bluetooth/hci_conn.c:3036 hci_num_comp_pkts_evt+0x1c8/0xa50 net/bluetooth/hci_event.c:4404 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/source/fuzzing/kernel/kasan/linux-6.16-rc7/arch/x86/entry/entry_64.S:245 </TASK>

Allocated by task 54: 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 le_conn_complete_evt+0x3d6/0x1220 net/bluetooth/hci_event.c:5628 hci_le_enh_conn_complete_evt+0x189/0x470 net/bluetooth/hci_event.c:5794 hci_event_func net/bluetooth/hci_event.c:7474 [inline] hci_event_packet+0x78c/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/source/fuzzing/kernel/kasan/linux-6.16-rc7/arch/x86/entry/entry_64.S:245

Freed by task 9572: 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_abort_conn_sync+0x5d1/0xdf0 net/bluetooth/hci_sync.c:5689 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

AnalysisAI

Use-after-free in the Linux kernel Bluetooth stack (net/bluetooth/hci_conn.c) allows an in-range attacker to corrupt kernel memory when the host processes an HCI_EV_NUM_COMP_PKTS event without properly locking hdev, letting hci_conn_tx_dequeue read a connection object already freed by a concurrent hci_conn_del/abort path. The flaw was found via KASAN fuzzing on kernel 6.16-rc7 and is fixed upstream; there is no public exploit identified at time of analysis and EPSS risk is low (0.17%).

Technical ContextAI

The vulnerability lives in the kernel's HCI (Host Controller Interface) layer that mediates between the Bluetooth host and controller. When the controller reports HCI_EV_NUM_COMP_PKTS (Number of Completed Packets), hci_num_comp_pkts_evt() calls hci_conn_tx_dequeue() on a per-connection structure allocated by __hci_conn_add() (kzalloc). Because the hdev device was not held/locked during event processing, a concurrent command-sync worker running hci_abort_conn_sync() -> hci_conn_del() -> hci_conn_cleanup() can drop the final kobject reference and kfree the hci_conn while the RX work path still dereferences it - a classic use-after-free (CWE-416) rooted in a missing-lock race condition (CWE-362). The KASAN report confirms the freed 4-byte read at hci_conn.c:3036. The stack traces show the allocating path (LE enhanced connection complete) and the freeing path (connection abort) running on different workqueues (hci_rx_work vs hci_cmd_sync_work), which is the concurrency window the fix closes.

Affected ProductsAI

The Linux kernel Bluetooth subsystem is affected; the bug was reproduced on 6.16-rc7 and fixed via stable-tree commits 2e128683176a56459cef8705fc7c35f438f88abd and dde33124f17cf3bab4dc5e18d1b4dee128361061 (https://git.kernel.org/stable/c/2e128683176a56459cef8705fc7c35f438f88abd and https://git.kernel.org/stable/c/dde33124f17cf3bab4dc5e18d1b4dee128361061). No CPE strings were provided in the intelligence, so exact backported version ranges are not enumerated here; affected builds are any kernel containing the hci_conn_tx_dequeue TX-queue code path prior to these fixes with CONFIG_BT enabled. Downstream distribution kernels inherit the flaw until they pick up the stable backports.

RemediationAI

Upstream fix available (PR/commit); released patched version not independently confirmed - apply the stable-tree commits 2e128683176a56459cef8705fc7c35f438f88abd and dde33124f17cf3bab4dc5e18d1b4dee128361061 (git.kernel.org/stable/c/...) or update to the distribution kernel package that incorporates them, then reboot. If patching must be deferred, the most effective compensating control is to disable Bluetooth where it is not required - unload the stack with 'modprobe -r btusb bluetooth' or block the modules, and disable/stop the bluetooth service (systemctl disable --now bluetooth); the trade-off is total loss of Bluetooth functionality (keyboards, audio, BLE peripherals). Where Bluetooth is needed, reduce exposure by keeping devices non-discoverable and out of pairing/connectable mode in untrusted physical environments, accepting that this only shrinks the attack window rather than closing the race. Confirm your distro's advisory for the exact fixed package version before relying on a version number.

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Vendor StatusVendor

SUSE

Severity: Moderate
Product Status
SUSE Liberty Linux 10 Fixed
SUSE Liberty Linux 9 Fixed
SUSE Linux Enterprise Desktop 15 SP7 Not-Affected
SUSE Linux Enterprise Desktop 15 SP7 Not-Affected
SUSE Linux Enterprise High Availability Extension 15 SP7 Not-Affected

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CVE-2025-39983 vulnerability details – vuln.today
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