# CVE-2026-63956: USB: serial: cypress_m8: fix memory corruption with small endpoint

> A malicious USB device can trigger memory corruption in the Linux kernel cypress_m8 driver, potentially leading to code execution or system crash.

- **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:** 19 Jul 2026
- **Updated:** 19 Jul 2026
- **Also known as:** BELL-CVE-2026-63956, DEBIAN-CVE-2026-63956, GHSA-4m78-mjgq-hq8g, ROOT-OS-UBUNTU-2204-CVE-2026-63956, UBUNTU-CVE-2026-63956

## What is CVE-2026-63956?

CVE-2026-63956 is a memory corruption vulnerability in Linux, published on 19 Jul 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:

USB: serial: cypress_m8: fix memory corruption with small endpoint

Make sure that the interrupt-out endpoint max packet size is at least
eight bytes to avoid user-controlled slab corruption or NULL-pointer
dereference should a malicious device report a smaller size.

## Which versions are affected by CVE-2026-63956?


## How do I fix CVE-2026-63956?

Apply the vendor's patch.

## Is CVE-2026-63956 being exploited?

There is no known exploitation of CVE-2026-63956 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-63956 and fix it if it is affected.

What it is: CVE-2026-63956 is a memory corruption vulnerability in Linux, published on 19 Jul 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-2026-63956 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-2026-63956/ (Markdown: https://insights.sbomify.com/CVE-2026-63956/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-63956
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-63956
- OSV: https://osv.dev/vulnerability/CVE-2026-63956

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-63956/
Summaries are generated and may contain mistakes; the official description above is the record.