# CVE-2025-23134: ALSA: timer: Don't take register_mutex with copy_from/to_user()

> A locking error in the Linux kernel ALSA timer subsystem can cause deadlocks, leading to a denial of service.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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:** 16 Apr 2025
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2025-23134, DEBIAN-CVE-2025-23134, GHSA-gxg5-6xg7-gc7q, UBUNTU-CVE-2025-23134

## What is CVE-2025-23134?

CVE-2025-23134 is a medium-severity vulnerability in Linux kernel, published on 16 Apr 2025. 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: timer: Don't take register_mutex with copy_from/to_user()

The infamous mmap_lock taken in copy_from/to_user() can be often
problematic when it's called inside another mutex, as they might lead
to deadlocks.

In the case of ALSA timer code, the bad pattern is with
guard(mutex)(&register_mutex) that covers copy_from/to_user() -- which
was mistakenly introduced at converting to guard(), and it had been
carefully worked around in the past.

This patch fixes those pieces simply by moving copy_from/to_user() out
of the register mutex lock again.

Weakness: CWE-667 (Improper Locking)

## Which versions are affected by CVE-2025-23134?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2025-23134?

Apply the vendor's patch.

## Is CVE-2025-23134 being exploited?

There is no known exploitation of CVE-2025-23134 in the wild and no public exploit code.

Public exploit code:

- The ASN1_STRING_set() function takes an `int` length, make sure the argument is not inadvertently truncated when it is called from asn1_ex_c2i(). (github_poc): https://github.com/thrilokh-q123/CVE-2025-23134_fixes_code

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-23134 and fix it if it is affected.

What it is: CVE-2025-23134 is a medium-severity vulnerability in Linux kernel, published on 16 Apr 2025. 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-2025-23134 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2025-23134/ (Markdown: https://insights.sbomify.com/CVE-2025-23134/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-23134
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-23134
- OSV: https://osv.dev/vulnerability/CVE-2025-23134

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-23134/
Summaries are generated and may contain mistakes; the official description above is the record.