# CVE-2025-40002: thunderbolt: Fix use-after-free in tb_dp_dprx_work

> A use-after-free vulnerability in the Linux kernel Thunderbolt driver allows local attackers to execute arbitrary code or escalate privileges via a race condition.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 18 Oct 2025
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2025-40002, DEBIAN-CVE-2025-40002, GHSA-x82v-x9cm-j5mp, UBUNTU-CVE-2025-40002

## What is CVE-2025-40002?

CVE-2025-40002 is an use after free vulnerability in Linux, published on 18 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:

thunderbolt: Fix use-after-free in tb_dp_dprx_work

The original code relies on cancel_delayed_work() in tb_dp_dprx_stop(),
which does not ensure that the delayed work item tunnel->dprx_work has
fully completed if it was already running. This leads to use-after-free
scenarios where tb_tunnel is deallocated by tb_tunnel_put(), while
tunnel->dprx_work remains active and attempts to dereference tb_tunnel
in tb_dp_dprx_work().

A typical race condition is illustrated below:

CPU 0                            | CPU 1
tb_dp_tunnel_active()            |
  tb_deactivate_and_free_tunnel()| tb_dp_dprx_start()
    tb_tunnel_deactivate()       |   queue_delayed_work()
      tb_dp_activate()           |
        tb_dp_dprx_stop()        | tb_dp_dprx_work() //delayed worker
          cancel_delayed_work()  |
    tb_tunnel_put(tunnel);       |
                                 |   tunnel = container_of(...); //UAF
                                 |   tunnel-> //UAF

Replacing cancel_delayed_work() with cancel_delayed_work_sync() is
not feasible as it would introduce a deadlock: both tb_dp_dprx_work()
and the cleanup path acquire tb->lock, and cancel_delayed_work_sync()
would wait indefinitely for the work item that cannot proceed.

Instead, implement proper reference counting:
- If cancel_delayed_work() returns true (work is pending), we release
  the reference in the stop function.
- If it returns false (work is executing or already completed), the
  reference is released in delayed work function itself.

This ensures the tb_tunnel remains valid during work item execution
while preventing memory leaks.

This bug was found by static analysis.

## Which versions are affected by CVE-2025-40002?


## How do I fix CVE-2025-40002?

Apply the vendor's patch.

## Is CVE-2025-40002 being exploited?

There is no known exploitation of CVE-2025-40002 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-40002 and fix it if it is affected.

What it is: CVE-2025-40002 is an use after free vulnerability in Linux, published on 18 Oct 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-2025-40002 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-2025-40002/ (Markdown: https://insights.sbomify.com/CVE-2025-40002/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-40002
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-40002
- OSV: https://osv.dev/vulnerability/CVE-2025-40002

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-40002/
Summaries are generated and may contain mistakes; the official description above is the record.