# CVE-2025-40223: most: usb: Fix use-after-free in hdm_disconnect

> A use-after-free vulnerability in the Linux kernel's MOST USB driver allows local attackers to cause denial of service or potentially execute code via device disconnection.

- **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:** 4 Dec 2025
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2025-40223, DEBIAN-CVE-2025-40223, GHSA-jh7w-53hp-qjqh, ROOT-OS-DEBIAN-11-CVE-2025-40223, ROOT-OS-UBUNTU-2404-CVE-2025-40223, UBUNTU-CVE-2025-40223

## What is CVE-2025-40223?

CVE-2025-40223 is an use after free vulnerability in Linux, published on 4 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:

most: usb: Fix use-after-free in hdm_disconnect

hdm_disconnect() calls most_deregister_interface(), which eventually
unregisters the MOST interface device with device_unregister(iface->dev).
If that drops the last reference, the device core may call release_mdev()
immediately while hdm_disconnect() is still executing.

The old code also freed several mdev-owned allocations in
hdm_disconnect() and then performed additional put_device() calls.
Depending on refcount order, this could lead to use-after-free or
double-free when release_mdev() ran (or when unregister paths also
performed puts).

Fix by moving the frees of mdev-owned allocations into release_mdev(),
so they happen exactly once when the device is truly released, and by
dropping the extra put_device() calls in hdm_disconnect() that are
redundant after device_unregister() and most_deregister_interface().

This addresses the KASAN slab-use-after-free reported by syzbot in
hdm_disconnect(). See report and stack traces in the bug link below.

## Which versions are affected by CVE-2025-40223?


## How do I fix CVE-2025-40223?

Apply the vendor's patch.

## Is CVE-2025-40223 being exploited?

There is no known exploitation of CVE-2025-40223 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-40223 and fix it if it is affected.

What it is: CVE-2025-40223 is an use after free vulnerability in Linux, published on 4 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-2025-40223 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-2025-40223/ (Markdown: https://insights.sbomify.com/CVE-2025-40223/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-40223
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-40223
- OSV: https://osv.dev/vulnerability/CVE-2025-40223

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-40223/
Summaries are generated and may contain mistakes; the official description above is the record.