# CVE-2026-63959: usb: typec: tcpm/tcpci_maxim: validate header NDO against RX_BYTE_CNT

> A malicious USB port can cause the Linux kernel to read uninitialized stack memory, potentially leaking sensitive information.

- **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:** 19 Jul 2026
- **Updated:** 20 Jul 2026
- **Also known as:** AZL-92739, BELL-CVE-2026-63959, DEBIAN-CVE-2026-63959, GHSA-fwcg-qvj5-vv4j, ROOT-OS-DEBIAN-11-CVE-2026-63959, ROOT-OS-DEBIAN-12-CVE-2026-63959, ROOT-OS-UBUNTU-2204-CVE-2026-63959, UBUNTU-CVE-2026-63959

## What is CVE-2026-63959?

CVE-2026-63959 is a vulnerability in Linux, published on 19 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:

usb: typec: tcpm/tcpci_maxim: validate header NDO against RX_BYTE_CNT

A broken/malicious port can transmit a CRC-valid frame whose header
advertises up to seven data objects but whose body carries fewer than
that.  Check for this, and rightfully reject the message, instead of
reading from uninitialized stack memory.

## Which versions are affected by CVE-2026-63959?


## How do I fix CVE-2026-63959?

Apply the vendor's patch.

## Is CVE-2026-63959 being exploited?

There is no known exploitation of CVE-2026-63959 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-63959 and fix it if it is affected.

What it is: CVE-2026-63959 is a vulnerability in Linux, published on 19 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-2026-63959 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-2026-63959/ (Markdown: https://insights.sbomify.com/CVE-2026-63959/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-63959
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-63959
- OSV: https://osv.dev/vulnerability/CVE-2026-63959

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-63959/
Summaries are generated and may contain mistakes; the official description above is the record.