# CVE-2025-40085: ALSA: usb-audio: Fix NULL pointer deference in try_to_register_card

> A local attacker with physical access can cause a kernel crash by connecting a malicious USB audio device, leading to denial of service.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 29 Oct 2025
- **Updated:** 23 May 2026
- **Also known as:** AZL-69030, BELL-CVE-2025-40085, DEBIAN-CVE-2025-40085, GHSA-2cjq-ppmx-48x5, ROOT-OS-DEBIAN-12-CVE-2025-40085, ROOT-OS-DEBIAN-13-CVE-2025-40085, ROOT-OS-UBUNTU-2204-CVE-2025-40085, ROOT-OS-UBUNTU-2404-CVE-2025-40085, UBUNTU-CVE-2025-40085

## What is CVE-2025-40085?

CVE-2025-40085 is a vulnerability in Linux, published on 29 Oct 2025. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

ALSA: usb-audio: Fix NULL pointer deference in try_to_register_card

In try_to_register_card(), the return value of usb_ifnum_to_if() is
passed directly to usb_interface_claimed() without a NULL check, which
will lead to a NULL pointer dereference when creating an invalid
USB audio device. Fix this by adding a check to ensure the interface
pointer is valid before passing it to usb_interface_claimed().

## Which versions are affected by CVE-2025-40085?


## How do I fix CVE-2025-40085?

Apply the vendor's patch.

## Is CVE-2025-40085 being exploited?

There is no known exploitation of CVE-2025-40085 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-40085 and fix it if it is affected.

What it is: CVE-2025-40085 is a vulnerability in Linux, published on 29 Oct 2025. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2025-40085 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-2025-40085/ (Markdown: https://insights.sbomify.com/CVE-2025-40085/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-40085
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-40085
- OSV: https://osv.dev/vulnerability/CVE-2025-40085

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-40085/
Summaries are generated and may contain mistakes; the official description above is the record.