# CVE-2026-74499: ALSA: usb-audio: fix OOB write in snd_usbmidi_akai_output()

> A malicious USB device can trigger a heap out-of-bounds write in the Linux kernel ALSA USB MIDI driver, potentially allowing local privilege escalation or code execution.

- **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 Aug 2026
- **Updated:** 19 Aug 2026
- **Also known as:** AZL-96431, BELL-CVE-2026-74499, DEBIAN-CVE-2026-74499, GHSA-gghh-gc7f-jqch, UBUNTU-CVE-2026-74499

## What is CVE-2026-74499?

CVE-2026-74499 is a memory corruption vulnerability in Linux, published on 15 Aug 2026. 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 OOB write in snd_usbmidi_akai_output()

snd_usbmidi_akai_output() computes its fill-loop bound

	buf_end = ep->max_transfer - MAX_AKAI_SYSEX_LEN - 1;

as a signed int, so a small device-advertised bulk-OUT max_transfer
makes buf_end negative.  The loop guard then compares the u32
urb->transfer_buffer_length against that negative int: the usual
arithmetic conversion turns buf_end into a large unsigned value, so the
guard stays true and each iteration keeps appending SysEx framing and
payload bytes past the end of the URB transfer buffer, which is only
max_transfer bytes long.

A USB device that advertises a tiny bulk-OUT endpoint can therefore
trigger an attacker-length- and content-controlled heap out-of-bounds
write when a process writes to the created /dev/snd/midiC*D* node.

Return early when there is no room for even one SysEx, so the loop is
never entered with a bound that would wrap.  The loop is the last
statement of the function, so bailing out is equivalent to it not
running.

Discovered by XBOW, triaged by Baul Lee <baul.lee@xbow.com>

## Which versions are affected by CVE-2026-74499?


## How do I fix CVE-2026-74499?

Apply the vendor's patch.

## Is CVE-2026-74499 being exploited?

There is no known exploitation of CVE-2026-74499 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74499 and fix it if it is affected.

What it is: CVE-2026-74499 is a memory corruption vulnerability in Linux, published on 15 Aug 2026. 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-2026-74499 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-2026-74499/ (Markdown: https://insights.sbomify.com/CVE-2026-74499/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74499
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74499
- OSV: https://osv.dev/vulnerability/CVE-2026-74499

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74499/
Summaries are generated and may contain mistakes; the official description above is the record.