# CVE-2025-39997: ALSA: usb-audio: fix race condition to UAF in snd_usbmidi_free

> A race condition in the Linux kernel's USB audio driver allows local attackers to trigger a use-after-free, potentially leading to code execution or privilege escalation.

- **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:** 15 Oct 2025
- **Updated:** 15 Oct 2026
- **Also known as:** BELL-CVE-2025-39997, DEBIAN-CVE-2025-39997, GHSA-xc3r-7j5x-74w4, UBUNTU-CVE-2025-39997

## What is CVE-2025-39997?

CVE-2025-39997 is an use after free vulnerability in Linux, published on 15 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:

ALSA: usb-audio: fix race condition to UAF in snd_usbmidi_free

The previous commit 0718a78f6a9f ("ALSA: usb-audio: Kill timer properly at
removal") patched a UAF issue caused by the error timer.

However, because the error timer kill added in this patch occurs after the
endpoint delete, a race condition to UAF still occurs, albeit rarely.

Additionally, since kill-cleanup for urb is also missing, freed memory can
be accessed in interrupt context related to urb, which can cause UAF.

Therefore, to prevent this, error timer and urb must be killed before
freeing the heap memory.

## Which versions are affected by CVE-2025-39997?


## How do I fix CVE-2025-39997?

Apply the vendor's patch.

## Is CVE-2025-39997 being exploited?

There is no known exploitation of CVE-2025-39997 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-39997 and fix it if it is affected.

What it is: CVE-2025-39997 is an use after free vulnerability in Linux, published on 15 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-2025-39997 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-2025-39997/ (Markdown: https://insights.sbomify.com/CVE-2025-39997/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-39997
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-39997
- OSV: https://osv.dev/vulnerability/CVE-2025-39997

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-39997/
Summaries are generated and may contain mistakes; the official description above is the record.