# CVE-2025-39860: Bluetooth: Fix use-after-free in l2cap_sock_cleanup_listen()

> A race condition in the Linux kernel Bluetooth subsystem allows local attackers to trigger a use-after-free, potentially leading to code execution or privilege escalation.

- **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:** 19 Sep 2025
- **Updated:** 15 Oct 2026
- **Also known as:** AZL-67559, AZL-74918, BELL-CVE-2025-39860, DEBIAN-CVE-2025-39860, GHSA-c684-q9wg-vhh9, ROOT-OS-DEBIAN-11-CVE-2025-39860, ROOT-OS-UBUNTU-2204-CVE-2025-39860, ROOT-OS-UBUNTU-2404-CVE-2025-39860, UBUNTU-CVE-2025-39860

## What is CVE-2025-39860?

CVE-2025-39860 is a high-severity use after free vulnerability in Debian Debian Linux, published on 19 Sep 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: Fix use-after-free in l2cap_sock_cleanup_listen()

syzbot reported the splat below without a repro.

In the splat, a single thread calling bt_accept_dequeue() freed sk
and touched it after that.

The root cause would be the racy l2cap_sock_cleanup_listen() call
added by the cited commit.

bt_accept_dequeue() is called under lock_sock() except for
l2cap_sock_release().

Two threads could see the same socket during the list iteration
in bt_accept_dequeue():

  CPU1                        CPU2 (close())
  ----                        ----
  sock_hold(sk)               sock_hold(sk);
  lock_sock(sk)   <-- block close()
  sock_put(sk)
  bt_accept_unlink(sk)
    sock_put(sk)  <-- refcnt by bt_accept_enqueue()
  release_sock(sk)
                              lock_sock(sk)
                              sock_put(sk)
                              bt_accept_unlink(sk)
                                sock_put(sk)        <-- last refcnt
                              bt_accept_unlink(sk)  <-- UAF

Depending on the timing, the other thread could show up in the
"Freed by task" part.

Let's call l2cap_sock_cleanup_listen() under lock_sock() in
l2cap_sock_release().

[0]:
BUG: KASAN: slab-use-after-free in debug_spin_lock_before kernel/locking/spinlock_debug.c:86 [inline]
BUG: KASAN: slab-use-after-free in do_raw_spin_lock+0x26f/0x2b0 kernel/locking/spinlock_debug.c:115
Read of size 4 at addr ffff88803b7eb1c4 by task syz.5.3276/16995
CPU: 3 UID: 0 PID: 16995 Comm: syz.5.3276 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xcd/0x630 mm/kasan/report.c:482
 kasan_report+0xe0/0x110 mm/kasan/report.c:595
 debug_spin_lock_before kernel/locking/spinlock_debug.c:86 [inline]
 do_raw_spin_lock+0x26f/0x2b0 kernel/locking/spinlock_debug.c:115
 spin_lock_bh include/linux/spinlock.h:356 [inline]
 release_sock+0x21/0x220 net/core/sock.c:3746
 bt_accept_dequeue+0x505/0x600 net/bluetooth/af_bluetooth.c:312
 l2cap_sock_cleanup_listen+0x5c/0x2a0 net/bluetooth/l2cap_sock.c:1451
 l2cap_sock_release+0x5c/0x210 net/bluetooth/l2cap_sock.c:1425
 __sock_release+0xb3/0x270 net/socket.c:649
 sock_close+0x1c/0x30 net/socket.c:1439
 __fput+0x3ff/0xb70 fs/file_table.c:468
 task_work_run+0x14d/0x240 kernel/task_work.c:227
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 exit_to_user_mode_loop+0xeb/0x110 kernel/entry/common.c:43
 exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
 do_syscall_64+0x3f6/0x4c0 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f2accf8ebe9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffdb6cb1378 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00000000000426fb RCX: 00007f2accf8ebe9
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007f2acd1b7da0 R08: 0000000000000001 R09: 00000012b6cb166f
R10: 0000001b30e20000 R11: 0000000000000246 R12: 00007f2acd1b609c
R13: 00007f2acd1b6090 R14: ffffffffffffffff R15: 00007ffdb6cb1490
 </TASK>

Allocated by task 5326:
 kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
 kasan_save_track+0x14/0x30 mm/kasan/common.c:68
 poison_kmalloc_redzone mm/kasan/common.c:388 [inline]
 __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:405
 kasan_kmalloc include/linux/kasan.h:260 [inline]
 __do_kmalloc_node mm/slub.c:4365 [inline]
 __kmalloc_nopro
---truncated---

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2025-39860?

It affects 2 products.


Products: Debian Debian Linux, Linux kernel.

## How do I fix CVE-2025-39860?

Apply the vendor's patch.

## Is CVE-2025-39860 being exploited?

There is no known exploitation of CVE-2025-39860 in the wild and no public exploit code.

## Other vulnerabilities in Debian Debian Linux

- [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild)
- [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild)
- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-39860 and fix it if it is affected.

What it is: CVE-2025-39860 is a high-severity use after free vulnerability in Debian Debian Linux, published on 19 Sep 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-2025-39860 in the wild and no public exploit code.

Affected product: Debian Debian 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-2025-39860/ (Markdown: https://insights.sbomify.com/CVE-2025-39860/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-39860
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-39860
- OSV: https://osv.dev/vulnerability/CVE-2025-39860

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-39860/
Summaries are generated and may contain mistakes; the official description above is the record.