# CVE-2025-40284: Bluetooth: MGMT: cancel mesh send timer when hdev removed

> A use-after-free vulnerability in the Linux kernel Bluetooth MGMT subsystem allows a local attacker to cause a system crash by triggering a timer after device removal.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/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:** 6 Dec 2025
- **Updated:** 15 Oct 2026
- **Also known as:** BELL-CVE-2025-40284, DEBIAN-CVE-2025-40284, GHSA-5w6m-vxmj-7w4c, ROOT-OS-DEBIAN-12-CVE-2025-40284, ROOT-OS-DEBIAN-13-CVE-2025-40284, ROOT-OS-UBUNTU-2204-CVE-2025-40284, ROOT-OS-UBUNTU-2404-CVE-2025-40284, UBUNTU-CVE-2025-40284

## What is CVE-2025-40284?

CVE-2025-40284 is a high-severity use after free vulnerability in Linux, published on 6 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: MGMT: cancel mesh send timer when hdev removed

mesh_send_done timer is not canceled when hdev is removed, which causes
crash if the timer triggers after hdev is gone.

Cancel the timer when MGMT removes the hdev, like other MGMT timers.

Should fix the BUG: sporadically seen by BlueZ test bot
(in "Mesh - Send cancel - 1" test).

Log:
------
BUG: KASAN: slab-use-after-free in run_timer_softirq+0x76b/0x7d0
...
Freed by task 36:
 kasan_save_stack+0x24/0x50
 kasan_save_track+0x14/0x30
 __kasan_save_free_info+0x3a/0x60
 __kasan_slab_free+0x43/0x70
 kfree+0x103/0x500
 device_release+0x9a/0x210
 kobject_put+0x100/0x1e0
 vhci_release+0x18b/0x240
------

## Which versions are affected by CVE-2025-40284?


## How do I fix CVE-2025-40284?

Apply the vendor's patch.

## Is CVE-2025-40284 being exploited?

There is no known exploitation of CVE-2025-40284 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-40284 and fix it if it is affected.

What it is: CVE-2025-40284 is a high-severity use after free vulnerability in Linux, published on 6 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-2025-40284 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-2025-40284/ (Markdown: https://insights.sbomify.com/CVE-2025-40284/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-40284
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-40284
- OSV: https://osv.dev/vulnerability/CVE-2025-40284

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-40284/
Summaries are generated and may contain mistakes; the official description above is the record.