# CVE-2026-31729: usb: typec: ucsi: validate connector number in ucsi_notify_common()

> A malicious USB device can trigger an out-of-bounds array access in the Linux kernel UCSI driver, potentially leading to code execution or system crash.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 1 May 2026
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2026-31729, DEBIAN-CVE-2026-31729, GHSA-77q3-374v-8gp2, ROOT-OS-DEBIAN-11-CVE-2026-31729, ROOT-OS-DEBIAN-12-CVE-2026-31729, ROOT-OS-UBUNTU-2204-CVE-2026-31729, ROOT-OS-UBUNTU-2404-CVE-2026-31729, UBUNTU-CVE-2026-31729

## What is CVE-2026-31729?

CVE-2026-31729 is a high-severity memory corruption vulnerability in Linux kernel, published on 1 May 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: ucsi: validate connector number in ucsi_notify_common()

The connector number extracted from CCI via UCSI_CCI_CONNECTOR() is a
7-bit field (0-127) that is used to index into the connector array in
ucsi_connector_change(). However, the array is only allocated for the
number of connectors reported by the device (typically 2-4 entries).

A malicious or malfunctioning device could report an out-of-range
connector number in the CCI, causing an out-of-bounds array access in
ucsi_connector_change().

Add a bounds check in ucsi_notify_common(), the central point where CCI
is parsed after arriving from hardware, so that bogus connector numbers
are rejected before they propagate further.

Weakness: CWE-129 (Improper Validation of Array Index)

## Which versions are affected by CVE-2026-31729?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-31729?

Apply the vendor's patch.

## Is CVE-2026-31729 being exploited?

There is no known exploitation of CVE-2026-31729 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-31729 and fix it if it is affected.

What it is: CVE-2026-31729 is a high-severity memory corruption vulnerability in Linux kernel, published on 1 May 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-2026-31729 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2026-31729/ (Markdown: https://insights.sbomify.com/CVE-2026-31729/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-31729
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-31729
- OSV: https://osv.dev/vulnerability/CVE-2026-31729

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-31729/
Summaries are generated and may contain mistakes; the official description above is the record.