# CVE-2026-89736: usb: gadget: u_audio: Fix use-after-free on sound card disconnect

> A use-after-free in the Linux kernel USB audio gadget allows local attackers to cause memory corruption and potentially execute code or escalate privileges.

- **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:** 11 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-100683, BELL-CVE-2026-89736, DEBIAN-CVE-2026-89736, GHSA-hjw3-qcfv-9g4p, UBUNTU-CVE-2026-89736

## What is CVE-2026-89736?

CVE-2026-89736 is a high-severity use after free vulnerability in Linux, published on 11 Sep 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: u_audio: Fix use-after-free on sound card disconnect

g_audio_cleanup() invokes snd_card_free_when_closed() to initiate sound
card teardown and immediately frees the underlying struct snd_uac_chip
context. However, snd_card_free_when_closed() returns asynchronously
while ALSA control elements (kctls) remain open in userspace.

When userspace control applications access or close these open file
descriptors, kctl callbacks attempt to dereference kctl->private_data
pointing to &uac->c_prm or &uac->p_prm within the freed uac structure,
resulting in a use-after-free (UAF) memory corruption.

Fix this issue by deferring the destruction of struct snd_uac_chip until
all references to the ALSA sound card are released. Register a custom
card->private_free callback (u_audio_card_free) during g_audio_setup()
that frees uac and its associated playback/capture request and ring
buffers only when the sound card reference count drops to zero.

## Which versions are affected by CVE-2026-89736?


## How do I fix CVE-2026-89736?

Apply the vendor's patch.

## Is CVE-2026-89736 being exploited?

There is no known exploitation of CVE-2026-89736 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89736 and fix it if it is affected.

What it is: CVE-2026-89736 is a high-severity use after free vulnerability in Linux, published on 11 Sep 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-2026-89736 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-2026-89736/ (Markdown: https://insights.sbomify.com/CVE-2026-89736/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89736
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89736
- OSV: https://osv.dev/vulnerability/CVE-2026-89736

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89736/
Summaries are generated and may contain mistakes; the official description above is the record.