# CVE-2025-40309: Bluetooth: SCO: Fix UAF on sco_conn_free

> A use-after-free vulnerability in the Linux kernel Bluetooth SCO subsystem allows attackers to execute arbitrary code or escalate privileges.

- **Severity:** High 8.0 (`CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 8 Dec 2025
- **Updated:** 15 Oct 2026
- **Also known as:** BELL-CVE-2025-40309, DEBIAN-CVE-2025-40309, GHSA-gj62-7ff7-xcwq, ROOT-OS-DEBIAN-12-CVE-2025-40309, ROOT-OS-DEBIAN-13-CVE-2025-40309, ROOT-OS-UBUNTU-2204-CVE-2025-40309, ROOT-OS-UBUNTU-2404-CVE-2025-40309, UBUNTU-CVE-2025-40309

## What is CVE-2025-40309?

CVE-2025-40309 is a high-severity use after free vulnerability in Linux, published on 8 Dec 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: SCO: Fix UAF on sco_conn_free

BUG: KASAN: slab-use-after-free in sco_conn_free net/bluetooth/sco.c:87 [inline]
BUG: KASAN: slab-use-after-free in kref_put include/linux/kref.h:65 [inline]
BUG: KASAN: slab-use-after-free in sco_conn_put+0xdd/0x410
net/bluetooth/sco.c:107
Write of size 8 at addr ffff88811cb96b50 by task kworker/u17:4/352

CPU: 1 UID: 0 PID: 352 Comm: kworker/u17:4 Not tainted
6.17.0-rc5-g717368f83676 #4 PREEMPT(voluntary)
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
Workqueue: hci13 hci_cmd_sync_work
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x10b/0x170 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0x191/0x550 mm/kasan/report.c:482
 kasan_report+0xc4/0x100 mm/kasan/report.c:595
 sco_conn_free net/bluetooth/sco.c:87 [inline]
 kref_put include/linux/kref.h:65 [inline]
 sco_conn_put+0xdd/0x410 net/bluetooth/sco.c:107
 sco_connect_cfm+0xb4/0xae0 net/bluetooth/sco.c:1441
 hci_connect_cfm include/net/bluetooth/hci_core.h:2082 [inline]
 hci_conn_failed+0x20a/0x2e0 net/bluetooth/hci_conn.c:1313
 hci_conn_unlink+0x55f/0x810 net/bluetooth/hci_conn.c:1121
 hci_conn_del+0xb6/0x1110 net/bluetooth/hci_conn.c:1147
 hci_abort_conn_sync+0x8c5/0xbb0 net/bluetooth/hci_sync.c:5689
 hci_cmd_sync_work+0x281/0x380 net/bluetooth/hci_sync.c:332
 process_one_work kernel/workqueue.c:3236 [inline]
 process_scheduled_works+0x77e/0x1040 kernel/workqueue.c:3319
 worker_thread+0xbee/0x1200 kernel/workqueue.c:3400
 kthread+0x3c7/0x870 kernel/kthread.c:463
 ret_from_fork+0x13a/0x1e0 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Allocated by task 31370:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x30/0x70 mm/kasan/common.c:68
 poison_kmalloc_redzone mm/kasan/common.c:388 [inline]
 __kasan_kmalloc+0x82/0x90 mm/kasan/common.c:405
 kasan_kmalloc include/linux/kasan.h:260 [inline]
 __do_kmalloc_node mm/slub.c:4382 [inline]
 __kmalloc_noprof+0x22f/0x390 mm/slub.c:4394
 kmalloc_noprof include/linux/slab.h:909 [inline]
 sk_prot_alloc+0xae/0x220 net/core/sock.c:2239
 sk_alloc+0x34/0x5a0 net/core/sock.c:2295
 bt_sock_alloc+0x3c/0x330 net/bluetooth/af_bluetooth.c:151
 sco_sock_alloc net/bluetooth/sco.c:562 [inline]
 sco_sock_create+0xc0/0x350 net/bluetooth/sco.c:593
 bt_sock_create+0x161/0x3b0 net/bluetooth/af_bluetooth.c:135
 __sock_create+0x3ad/0x780 net/socket.c:1589
 sock_create net/socket.c:1647 [inline]
 __sys_socket_create net/socket.c:1684 [inline]
 __sys_socket+0xd5/0x330 net/socket.c:1731
 __do_sys_socket net/socket.c:1745 [inline]
 __se_sys_socket net/socket.c:1743 [inline]
 __x64_sys_socket+0x7a/0x90 net/socket.c:1743
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc7/0x240 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 31374:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x30/0x70 mm/kasan/common.c:68
 kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:576
 poison_slab_object mm/kasan/common.c:243 [inline]
 __kasan_slab_free+0x3d/0x50 mm/kasan/common.c:275
 kasan_slab_free include/linux/kasan.h:233 [inline]
 slab_free_hook mm/slub.c:2428 [inline]
 slab_free mm/slub.c:4701 [inline]
 kfree+0x199/0x3b0 mm/slub.c:4900
 sk_prot_free net/core/sock.c:2278 [inline]
 __sk_destruct+0x4aa/0x630 net/core/sock.c:2373
 sco_sock_release+0x2ad/0x300 net/bluetooth/sco.c:1333
 __sock_release net/socket.c:649 [inline]
 sock_close+0xb8/0x230 net/socket.c:1439
 __fput+0x3d1/0x9e0 fs/file_table.c:468
 task_work_run+0x206/0x2a0 kernel/task_work.c:227
 get_signal+0x1201/0x1410 kernel/signal.c:2807
 arch_do_signal_or_restart+0x34/0x740 arch/x86/kernel/signal.c:337
 exit_to_user_mode_loop+0x68/0xc0 kernel/entry/common.c:40
 exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
 s
---truncated---

## Which versions are affected by CVE-2025-40309?


## How do I fix CVE-2025-40309?

Apply the vendor's patch.

## Is CVE-2025-40309 being exploited?

There is no known exploitation of CVE-2025-40309 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-40309 and fix it if it is affected.

What it is: CVE-2025-40309 is a high-severity use after free vulnerability in Linux, published on 8 Dec 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2025-40309 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2025-40309/ (Markdown: https://insights.sbomify.com/CVE-2025-40309/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-40309
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-40309
- OSV: https://osv.dev/vulnerability/CVE-2025-40309

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-40309/
Summaries are generated and may contain mistakes; the official description above is the record.