# CVE-2026-80970: ALSA: FCP: do not copy out an uninitialised init response

> A local attacker can read uninitialized kernel memory via the ALSA FCP driver, potentially exposing sensitive kernel data.

- **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:** 11 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-80970, DEBIAN-CVE-2026-80970, GHSA-x4cq-72c3-qv9j, UBUNTU-CVE-2026-80970

## What is CVE-2026-80970?

CVE-2026-80970 is a 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: FCP: do not copy out an uninitialised init response

fcp_ioctl_init() allocates its response buffer with kmalloc() and copies
the whole buffer back to userspace:

	buf_size = init.step0_resp_size + init.step2_resp_size;

	void *resp __free(kfree) =
		kmalloc(buf_size, GFP_KERNEL);
	...
	if (copy_to_user(arg->resp, resp, buf_size))
		return -EFAULT;

Nothing clears the buffer, and the only writer of its leading
step0_resp_size bytes is the step-0 control transfer:

	err = snd_usb_ctl_msg(dev, usb_rcvctrlpipe(dev, 0),
		FCP_USB_REQ_STEP0,
		USB_RECIP_INTERFACE | USB_TYPE_CLASS | USB_DIR_IN,
		0, private->bInterfaceNumber,
		step0_resp, private->step0_resp_size);
	if (err < 0)
		return err;

usb_fill_control_urb() does not set URB_SHORT_NOT_OK, so a short or
zero-length data stage completes with status 0 and snd_usb_ctl_msg()
returns a small actual_length.  The only check is err < 0, so a short
transfer is accepted as success.

snd_usb_ctl_msg() copies the full size back unconditionally:

	buf = kmemdup(data, size, GFP_KERNEL);
	...
	memcpy(data, buf, size);

Bytes the device never wrote are therefore restored into resp unchanged
and copied to userspace.  step0_resp_size and step2_resp_size are each
validated only to 1..255, so the caller also picks the slab cache, from
kmalloc-8 up to kmalloc-512.

On 7.2.0-rc5 (arm64), device answering step 0 with a zero-length data
stage, s0 = s2 = 255:

  # init_on_alloc off, no spray
  step0 window [0,255): nonzero=94/255
  000: 00 80 60 06 00 00 ff ff 18 00 00 00 57 01 ea 01
  010: 08 78 22 13 00 00 ff ff a8 c4 5f 80 00 80 ff ff

  # same kernel, kmalloc-512 pre-seeded with an 8-byte tag
  step0 window [0,255): nonzero=219/255  tagbytes=232

  # identical run, init_on_alloc=1
  step0 window [0,255): nonzero=0/255  tagbytes=0

  # all three runs
  step2 window [255,510): device words matched=62/62

a8 c4 5f 80 00 80 ff ff is the little-endian kernel text address
ffff8000805fc4a8.  The step-2 window is unaffected, so the disclosure is
exactly the step-0 region.

Zero the buffer, and require the step-0 transfer to deliver the full
step0_resp_size bytes so a short data stage is reported as an error.

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

## Which versions are affected by CVE-2026-80970?


## How do I fix CVE-2026-80970?

Apply the vendor's patch.

## Is CVE-2026-80970 being exploited?

There is no known exploitation of CVE-2026-80970 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-80970 and fix it if it is affected.

What it is: CVE-2026-80970 is a 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-2026-80970 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-2026-80970/ (Markdown: https://insights.sbomify.com/CVE-2026-80970/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-80970
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-80970
- OSV: https://osv.dev/vulnerability/CVE-2026-80970

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-80970/
Summaries are generated and may contain mistakes; the official description above is the record.