# CVE-2026-90033: ALSA: usb-audio: fix OOB write in snd_usbmidi_us122l_output()

> A local attacker with physical access can trigger an out-of-bounds write in the Linux kernel USB MIDI driver, 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:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 16 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-101543, BELL-CVE-2026-90033, DEBIAN-CVE-2026-90033, GHSA-3999-x38p-c9qg, UBUNTU-CVE-2026-90033

## What is CVE-2026-90033?

CVE-2026-90033 is a memory corruption vulnerability in Linux, published on 16 Sep 2026. 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 OOB write in snd_usbmidi_us122l_output()

The snd_usbmidi_us122l_output() picks a count of 2 on anything slower
than high speed and never relates it to ep->max_transfer.  The URB
buffer holds exactly max_transfer bytes, so a device declaring a one
byte bulk endpoint takes two bytes from snd_rawmidi_transmit(), and the
memset that pads the rest computes 1 - 2 in int and wraps to SIZE_MAX.

Only 0x800e and 0x800f are pinned to nine bytes.  The US-122MKII at
0x0644:0x8021 falls to the default and takes usb_maxpacket(), which the
USB core only clamps downward.

The akai and novation output ops in this file were given the same guard
recently.  Do the same here.

## Which versions are affected by CVE-2026-90033?


## How do I fix CVE-2026-90033?

Apply the vendor's patch.

## Is CVE-2026-90033 being exploited?

There is no known exploitation of CVE-2026-90033 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-90033 and fix it if it is affected.

What it is: CVE-2026-90033 is a memory corruption vulnerability in Linux, published on 16 Sep 2026. 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-2026-90033 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-2026-90033/ (Markdown: https://insights.sbomify.com/CVE-2026-90033/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-90033
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-90033
- OSV: https://osv.dev/vulnerability/CVE-2026-90033

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-90033/
Summaries are generated and may contain mistakes; the official description above is the record.