# CVE-2026-97931: ALSA: us122l: Prevent write upgrades for read mappings

> A local attacker with access to the hwdep node can escalate privileges or execute code by exploiting a memory mapping permission flaw in the ALSA us122l driver.

- **Severity:** High 7.0 (`CVSS:3.1/AV:L/AC:H/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:** 25 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-104823, BELL-CVE-2026-97931, DEBIAN-CVE-2026-97931, GHSA-vp4m-4hj6-cc9p, UBUNTU-CVE-2026-97931

## What is CVE-2026-97931?

CVE-2026-97931 is a high-severity vulnerability in Linux, published on 25 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: us122l: Prevent write upgrades for read mappings

The hwdep mmap callback rejects read-buffer mappings that are initially
writable, but leaves VM_MAYWRITE set on mappings created with PROT_READ.
A process that can open the hwdep node O_RDWR can later use mprotect() to
make the mapping writable.

The read allocation begins with struct usb_stream. Its read_size member is
used by the fault handler to decide which pages belong to the read buffer.
The read VMA intentionally remains expandable because pcm_usb_stream uses
mremap() after reading that size. Changing read_size first can therefore
map and access pages beyond the allocation. The same member is also
consumed by usb_stream_free(), where changing it can make
free_pages_exact() release pages outside the allocation.

Clear VM_MAYWRITE for read-buffer mappings after rejecting an initially
writable VMA. This keeps the separate output-buffer mapping writable while
preventing later permission upgrades.

## Which versions are affected by CVE-2026-97931?


## How do I fix CVE-2026-97931?

Apply the vendor's patch.

## Is CVE-2026-97931 being exploited?

There is no known exploitation of CVE-2026-97931 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-97931 and fix it if it is affected.

What it is: CVE-2026-97931 is a high-severity vulnerability in Linux, published on 25 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-2026-97931 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-2026-97931/ (Markdown: https://insights.sbomify.com/CVE-2026-97931/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-97931
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-97931
- OSV: https://osv.dev/vulnerability/CVE-2026-97931

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-97931/
Summaries are generated and may contain mistakes; the official description above is the record.