# CVE-2026-64584: usb: gadget: f_midi: cancel pending IN work before freeing the midi object

> A use-after-free in the Linux kernel USB MIDI gadget driver allows local attackers to execute code or escalate privileges via race conditions during device unbinding.

- **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:** 6 Aug 2026
- **Updated:** 19 Aug 2026
- **Also known as:** BELL-CVE-2026-64584, DEBIAN-CVE-2026-64584, GHSA-m3h2-47px-55rm, UBUNTU-CVE-2026-64584

## What is CVE-2026-64584?

CVE-2026-64584 is a high-severity use after free vulnerability in Linux, published on 6 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: gadget: f_midi: cancel pending IN work before freeing the midi object

The f_midi driver embeds a work item (midi->work) whose handler,
f_midi_in_work(), dereferences the enclosing struct f_midi through
container_of().  This work is armed from two sites: f_midi_complete(),
on a normal IN-endpoint completion, and f_midi_in_trigger(), on an ALSA
rawmidi output-stream start.

Neither f_midi_disable() nor f_midi_unbind() cancels midi->work.
f_midi_disable() only disables the endpoints and drains the in_req_fifo;
it does not synchronize the work item, and the sound card is released
asynchronously to the final free of the midi object.

The midi object is reference-counted (midi->free_ref) and is freed in
f_midi_free() only once both the usb_function reference and the rawmidi
private_data reference have been dropped.  In f_midi_unbind(),
f_midi_disable() runs before the sound card is released, so while the
USB endpoints are already disabled the rawmidi device is still usable by
an open substream.  A concurrent userspace write on such a substream can
reach f_midi_in_trigger() and queue midi->work again after
f_midi_disable() has returned.  A work item armed this way may still be
pending when the last reference drops and f_midi_free() proceeds to
kfree(midi), letting f_midi_in_work() dereference the struct after it
has been freed, a use-after-free.

For this reason cancelling midi->work in f_midi_disable() would not be
sufficient: the ALSA trigger path can rearm the work after disable()
returns.  Cancelling at the refcount-zero free site is the boundary
after which neither arming source can survive, because by then both
references that keep the midi object alive have been dropped: the USB
endpoints are already disabled and the rawmidi device has been released.

Fix this by calling cancel_work_sync(&midi->work) in the refcount-zero
block of f_midi_free(), before the embedded work_struct is freed along
with the rest of the structure.  opts->lock is a sleeping mutex, so
calling cancel_work_sync() under it is permitted, and the handler takes
midi->transmit_lock rather than opts->lock, so no self-deadlock can
occur while it waits for a running instance of the work to finish.

This issue was found by an in-house static analysis tool.

## Which versions are affected by CVE-2026-64584?


## How do I fix CVE-2026-64584?

Apply the vendor's patch.

## Is CVE-2026-64584 being exploited?

There is no known exploitation of CVE-2026-64584 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-64584 and fix it if it is affected.

What it is: CVE-2026-64584 is a high-severity use after free vulnerability in Linux, published on 6 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-2026-64584 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-2026-64584/ (Markdown: https://insights.sbomify.com/CVE-2026-64584/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-64584
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-64584
- OSV: https://osv.dev/vulnerability/CVE-2026-64584

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-64584/
Summaries are generated and may contain mistakes; the official description above is the record.