# CVE-2025-21835: usb: gadget: f_midi: fix MIDI Streaming descriptor lengths

> A Linux kernel USB gadget driver flaw leaks uninitialized stack memory to the host when MIDI port counts differ, requiring specific gadget configuration.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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:** 7 Mar 2025
- **Updated:** 15 Oct 2026
- **Also known as:** BELL-CVE-2025-21835, DEBIAN-CVE-2025-21835, GHSA-2x4w-2j26-p5hx, ROOT-OS-UBUNTU-2404-CVE-2025-21835, UBUNTU-CVE-2025-21835

## What is CVE-2025-21835?

CVE-2025-21835 is a medium-severity vulnerability in Linux kernel, published on 7 Mar 2025. 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: gadget: f_midi: fix MIDI Streaming descriptor lengths

While the MIDI jacks are configured correctly, and the MIDIStreaming
endpoint descriptors are filled with the correct information,
bNumEmbMIDIJack and bLength are set incorrectly in these descriptors.

This does not matter when the numbers of in and out ports are equal, but
when they differ the host will receive broken descriptors with
uninitialized stack memory leaking into the descriptor for whichever
value is smaller.

The precise meaning of "in" and "out" in the port counts is not clearly
defined and can be confusing.  But elsewhere the driver consistently
uses this to match the USB meaning of IN and OUT viewed from the host,
so that "in" ports send data to the host and "out" ports receive data
from it.

## Which versions are affected by CVE-2025-21835?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2025-21835?

Apply the vendor's patch.

## Is CVE-2025-21835 being exploited?

There is no known exploitation of CVE-2025-21835 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-2025-21835 and fix it if it is affected.

What it is: CVE-2025-21835 is a medium-severity vulnerability in Linux kernel, published on 7 Mar 2025. 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-2025-21835 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-2025-21835/ (Markdown: https://insights.sbomify.com/CVE-2025-21835/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-21835
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-21835
- OSV: https://osv.dev/vulnerability/CVE-2025-21835

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-21835/
Summaries are generated and may contain mistakes; the official description above is the record.