# CVE-2026-64487: ALSA: caiaq: fix out-of-bounds read in the Traktor Kontrol S4 input parser

> A malicious USB device can trigger an integer underflow in the ALSA caiaq driver, causing an out-of-bounds read and potential system crash or data leak.

- **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:** 25 Jul 2026
- **Updated:** 17 Aug 2026
- **Also known as:** AZL-93533, BELL-CVE-2026-64487, DEBIAN-CVE-2026-64487, GHSA-x4v5-hfh7-vrg5, ROOT-OS-UBUNTU-2204-CVE-2026-64487, UBUNTU-CVE-2026-64487

## What is CVE-2026-64487?

CVE-2026-64487 is a vulnerability in Linux, published on 25 Jul 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: caiaq: fix out-of-bounds read in the Traktor Kontrol S4 input parser

snd_usb_caiaq_tks4_dispatch() decodes the Traktor Kontrol S4 input
stream in fixed 16-byte (TKS4_MSGBLOCK_SIZE) message blocks. On every
iteration it advances buf and subtracts the block size while looping on
"while (len)".

len is urb->actual_length. That value is supplied by the device and is
not guaranteed to be a multiple of 16. When a final short block leaves
len between 1 and 15, the loop runs once more, reads up to buf[15], and
then does "len -= TKS4_MSGBLOCK_SIZE". As len is unsigned this underflows
to a huge value. The loop then keeps iterating and walking buf far past
the end of the 512-byte ep4_in_buf, reading out of bounds until a bogus
block id happens to be hit.

Iterate only while a full message block is available. This stops the
unsigned underflow and silently drops any trailing partial block, which
carries no complete control value anyway.

The sibling endpoint-4 parsers are not affected. The Traktor Kontrol X1
and Maschine arms in snd_usb_caiaq_ep4_reply_dispatch() floor
urb->actual_length before dispatching.

## Which versions are affected by CVE-2026-64487?


## How do I fix CVE-2026-64487?

Apply the vendor's patch.

## Is CVE-2026-64487 being exploited?

There is no known exploitation of CVE-2026-64487 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-64487 and fix it if it is affected.

What it is: CVE-2026-64487 is a vulnerability in Linux, published on 25 Jul 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-2026-64487 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-2026-64487/ (Markdown: https://insights.sbomify.com/CVE-2026-64487/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-64487
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-64487
- OSV: https://osv.dev/vulnerability/CVE-2026-64487

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-64487/
Summaries are generated and may contain mistakes; the official description above is the record.