# CVE-2026-74681: usb: misc: usbio: check ibuf_len against rxbuf_len in bulk msg

> A logic error in the Linux kernel USB IO driver compares buffer sizes incorrectly, potentially allowing buffer over-reads or denial of service via crafted USB messages.

- **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:** 22 Aug 2026
- **Updated:** 22 Aug 2026
- **Also known as:** BELL-CVE-2026-74681, DEBIAN-CVE-2026-74681, GHSA-c35q-c6r4-9764, UBUNTU-CVE-2026-74681

## What is CVE-2026-74681?

CVE-2026-74681 is a vulnerability in Linux, published on 22 Aug 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: misc: usbio: check ibuf_len against rxbuf_len in bulk msg

ibuf_len is the bulk IN (receive) buffer size, but the EMSGSIZE check
in usbio_bulk_msg() compares it against txbuf_len — the bulk OUT
endpoint size.  Both are taken independently from different endpoints
in usbio_probe(), so the check is wrong when they differ.

Use rxbuf_len for the IN direction.  This matches the buffer that
actually holds the response data.

## Which versions are affected by CVE-2026-74681?


## How do I fix CVE-2026-74681?

Apply the vendor's patch.

## Is CVE-2026-74681 being exploited?

There is no known exploitation of CVE-2026-74681 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74681 and fix it if it is affected.

What it is: CVE-2026-74681 is a vulnerability in Linux, published on 22 Aug 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-2026-74681 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-2026-74681/ (Markdown: https://insights.sbomify.com/CVE-2026-74681/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74681
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74681
- OSV: https://osv.dev/vulnerability/CVE-2026-74681

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74681/
Summaries are generated and may contain mistakes; the official description above is the record.