# CVE-2025-40269: ALSA: usb-audio: Fix potential overflow of PCM transfer buffer

> A buffer overflow in the Linux kernel USB audio driver allows attackers to cause denial of service or execute code via malicious USB descriptors.

- **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:** 5 Aug 2026
- **Also known as:** BELL-CVE-2025-40269, DEBIAN-CVE-2025-40269, GHSA-7g56-9fh3-wcxw, ROOT-OS-DEBIAN-12-CVE-2025-40269, ROOT-OS-DEBIAN-13-CVE-2025-40269, ROOT-OS-UBUNTU-2204-CVE-2025-40269, ROOT-OS-UBUNTU-2404-CVE-2025-40269, UBUNTU-CVE-2025-40269

## What is CVE-2025-40269?

CVE-2025-40269 is a high-severity memory corruption 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:

ALSA: usb-audio: Fix potential overflow of PCM transfer buffer

The PCM stream data in USB-audio driver is transferred over USB URB
packet buffers, and each packet size is determined dynamically.  The
packet sizes are limited by some factors such as wMaxPacketSize USB
descriptor.  OTOH, in the current code, the actually used packet sizes
are determined only by the rate and the PPS, which may be bigger than
the size limit above.  This results in a buffer overflow, as reported
by syzbot.

Basically when the limit is smaller than the calculated packet size,
it implies that something is wrong, most likely a weird USB
descriptor.  So the best option would be just to return an error at
the parameter setup time before doing any further operations.

This patch introduces such a sanity check, and returns -EINVAL when
the packet size is greater than maxpacksize.  The comparison with
ep->packsize[1] alone should suffice since it's always equal or
greater than ep->packsize[0].

## Which versions are affected by CVE-2025-40269?


## How do I fix CVE-2025-40269?

Apply the vendor's patch.

## Is CVE-2025-40269 being exploited?

There is no known exploitation of CVE-2025-40269 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-40269 and fix it if it is affected.

What it is: CVE-2025-40269 is a high-severity memory corruption 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-2025-40269 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-2025-40269/ (Markdown: https://insights.sbomify.com/CVE-2025-40269/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-40269
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-40269
- OSV: https://osv.dev/vulnerability/CVE-2025-40269

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-40269/
Summaries are generated and may contain mistakes; the official description above is the record.