# CVE-2026-93808: ALSA: usb-audio: caiaq: validate EP1 reply lengths

> A missing length validation in the Linux kernel's USB audio driver allows a local attacker to cause a denial of service via a malicious USB device.

- **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:** 24 Sep 2026
- **Updated:** 3 Oct 2026
- **Also known as:** AZL-103607, BELL-CVE-2026-93808, DEBIAN-CVE-2026-93808, GHSA-qcqv-jmh6-h97c, UBUNTU-CVE-2026-93808

## What is CVE-2026-93808?

CVE-2026-93808 is a denial of service vulnerability in Linux, published on 24 Sep 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: caiaq: validate EP1 reply lengths

usb_ep1_command_reply_dispatch() uses buf[0] as a command byte and then
reads command-specific fixed items from the same URB buffer. Several
paths use buf + 1, buf[1], buf[2], or buf + 3 without first proving that
urb->actual_length contains those bytes.

Add per-command length checks, use a payload length derived from the
bytes after the command byte for the control-state copy, and reject short
analog input payloads before the input helper reads fixed offsets from
the EP1 reply.

## Which versions are affected by CVE-2026-93808?


## How do I fix CVE-2026-93808?

Apply the vendor's patch.

## Is CVE-2026-93808 being exploited?

There is no known exploitation of CVE-2026-93808 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-93808 and fix it if it is affected.

What it is: CVE-2026-93808 is a denial of service vulnerability in Linux, published on 24 Sep 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-2026-93808 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-2026-93808/ (Markdown: https://insights.sbomify.com/CVE-2026-93808/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-93808
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-93808
- OSV: https://osv.dev/vulnerability/CVE-2026-93808

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-93808/
Summaries are generated and may contain mistakes; the official description above is the record.