# CVE-2026-80971: ALSA: bcd2000: clear the URB pointers on disconnect

> A use-after-free vulnerability in the ALSA bcd2000 driver allows attackers to cause memory corruption or system crashes via race conditions during device disconnection.

- **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-100503, BELL-CVE-2026-80971, DEBIAN-CVE-2026-80971, GHSA-27wq-xjr3-w8c9, UBUNTU-CVE-2026-80971

## What is CVE-2026-80971?

CVE-2026-80971 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:

ALSA: bcd2000: clear the URB pointers on disconnect

bcd2000_free_usb_related_resources() frees both URBs and leaves the
pointers behind:

	usb_kill_urb(bcd2k->midi_out_urb);
	usb_kill_urb(bcd2k->midi_in_urb);

	usb_free_urb(bcd2k->midi_out_urb);
	usb_free_urb(bcd2k->midi_in_urb);

The rawmidi device outlives that call.  A substream that is still open
when the device is unplugged reaches bcd2000_midi_send() from the
trigger path on close.  That function writes to the freed URB and then
hands it to the USB core:

	bcd2k->midi_out_urb->transfer_buffer_length = BUFSIZE;
	...
	ret = usb_submit_urb(bcd2k->midi_out_urb, GFP_ATOMIC);

usb_kill_urb() does not stop a later submission either, so a submit that
races the disconnect can requeue the URB after it has been reaped.
midi_in_urb is exposed the same way: bcd2000_input_complete() resubmits
it from the completion handler.

KASAN on 7.2.0-rc5 (arm64):

  BUG: KASAN: slab-use-after-free in bcd2000_midi_send [snd_bcd2000]
  Write of size 4 at addr ffff00001827d388 by task bpoc/168
   __asan_store4
   bcd2000_midi_send [snd_bcd2000]
   bcd2000_midi_output_trigger [snd_bcd2000]
   snd_rawmidi_kernel_write1
   close_substream.part.0
  Freed by task 168:
   usb_free_urb
   bcd2000_disconnect [snd_bcd2000]

  BUG: KASAN: slab-use-after-free in usb_submit_urb
  Read of size 8 at addr ffff00001827d3b8 by task bpoc/168

Clear both pointers after freeing and test them on the paths that can
still run.  Poison the URBs before freeing them: usb_poison_urb() waits
for a running completion handler and rejects any later submission, so
after it returns the input path is quiesced and only the rawmidi trigger
path can still reach bcd2000_midi_send().  No unpoison is needed; the
URBs are freed on the next line.

Discovered by XBOW, triaged by Baul Lee <baul.lee@xbow.com>

## Which versions are affected by CVE-2026-80971?


## How do I fix CVE-2026-80971?

Apply the vendor's patch.

## Is CVE-2026-80971 being exploited?

There is no known exploitation of CVE-2026-80971 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-80971 and fix it if it is affected.

What it is: CVE-2026-80971 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-2026-80971 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-2026-80971/ (Markdown: https://insights.sbomify.com/CVE-2026-80971/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-80971
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-80971
- OSV: https://osv.dev/vulnerability/CVE-2026-80971

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-80971/
Summaries are generated and may contain mistakes; the official description above is the record.