# CVE-2026-89881: media: rtl2832_sdr: use vb2_video_unregister_device() on remove to fix DMA leak

> A memory leak in the rtl2832_sdr driver allows local attackers to exhaust kernel memory by repeatedly connecting and disconnecting the device, causing denial of service.

- **Severity:** Not scored
- **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:** 16 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-101550, BELL-CVE-2026-89881, DEBIAN-CVE-2026-89881, GHSA-64c5-3gxh-7523, UBUNTU-CVE-2026-89881

## What is CVE-2026-89881?

CVE-2026-89881 is a memory corruption vulnerability in Linux, published on 16 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:

media: rtl2832_sdr: use vb2_video_unregister_device() on remove to fix DMA leak

rtl2832_sdr_remove() runs on USB disconnect and clears dev->udev to
NULL before any pending streaming teardown has run. When user space
later closes its file descriptor, vb2 calls rtl2832_sdr_stop_streaming()
which in turn calls rtl2832_sdr_free_stream_bufs(). That helper releases
each coherent buffer with:

    usb_free_coherent(dev->udev, dev->buf_size,
                      dev->buf_list[dev->buf_num],
                      dev->dma_addr[dev->buf_num]);

usb_free_coherent() returns immediately when its dev argument is NULL,
so every DMA stream buffer that was live at disconnect is silently
leaked. The URBs allocated in rtl2832_sdr_alloc_urbs() outlive the
device for the same reason.

The rtl2832_sdr driver uses vb2_fop_release() in its file_operations,
so replace video_unregister_device(&dev->vdev) with
vb2_video_unregister_device(&dev->vdev) and move it before clearing
dev->udev. vb2_video_unregister_device() releases the vb2 queue, which
synchronously runs rtl2832_sdr_stop_streaming() if streaming is active,
so URBs and coherent DMA stream buffers are freed while dev->udev is
still valid.

vb2_video_unregister_device() locks vdev->queue->lock (vb_queue_lock)
internally, and stop_streaming() locks v4l2_lock, so the previous outer
mutex_lock(&dev->vb_queue_lock) / mutex_lock(&dev->v4l2_lock) pair
around the unregister sequence would self-deadlock and has been removed.
A short v4l2_lock critical section around dev->udev = NULL remains so
any ioctl path that still holds the file descriptor sees coherent state.

Issue identified by automated review of the INV-003 series at
https://sashiko.dev/

## Which versions are affected by CVE-2026-89881?


## How do I fix CVE-2026-89881?

Apply the vendor's patch.

## Is CVE-2026-89881 being exploited?

There is no known exploitation of CVE-2026-89881 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89881 and fix it if it is affected.

What it is: CVE-2026-89881 is a memory corruption vulnerability in Linux, published on 16 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-2026-89881 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-2026-89881/ (Markdown: https://insights.sbomify.com/CVE-2026-89881/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89881
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89881
- OSV: https://osv.dev/vulnerability/CVE-2026-89881

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89881/
Summaries are generated and may contain mistakes; the official description above is the record.