# CVE-2025-38257: s390/pkey: Prevent overflow in size calculation for memdup_user()

> An integer overflow in the s390/pkey driver allows attackers to trigger memory corruption via a crafted ioctl call, potentially leading to code execution or system crashes.

- **Severity:** High 7.3 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:L/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:** 9 Jul 2025
- **Updated:** 15 Oct 2026
- **Also known as:** AZL-64871, BELL-CVE-2025-38257, DEBIAN-CVE-2025-38257, GHSA-wgwx-65v3-j243, ROOT-OS-DEBIAN-11-CVE-2025-38257, ROOT-OS-DEBIAN-12-CVE-2025-38257, ROOT-OS-UBUNTU-2204-CVE-2025-38257, ROOT-OS-UBUNTU-2404-CVE-2025-38257, UBUNTU-CVE-2025-38257

## What is CVE-2025-38257?

CVE-2025-38257 is a high-severity vulnerability in Debian Debian Linux, published on 9 Jul 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:

s390/pkey: Prevent overflow in size calculation for memdup_user()

Number of apqn target list entries contained in 'nr_apqns' variable is
determined by userspace via an ioctl call so the result of the product in
calculation of size passed to memdup_user() may overflow.

In this case the actual size of the allocated area and the value
describing it won't be in sync leading to various types of unpredictable
behaviour later.

Use a proper memdup_array_user() helper which returns an error if an
overflow is detected. Note that it is different from when nr_apqns is
initially zero - that case is considered valid and should be handled in
subsequent pkey_handler implementations.

Found by Linux Verification Center (linuxtesting.org).

## Which versions are affected by CVE-2025-38257?

It affects 2 products.


Products: Debian Debian Linux, Linux kernel.

## How do I fix CVE-2025-38257?

Apply the vendor's patch.

## Is CVE-2025-38257 being exploited?

There is no known exploitation of CVE-2025-38257 in the wild and no public exploit code.

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- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-38257 and fix it if it is affected.

What it is: CVE-2025-38257 is a high-severity vulnerability in Debian Debian Linux, published on 9 Jul 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-2025-38257 in the wild and no public exploit code.

Affected product: Debian Debian 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-2025-38257/ (Markdown: https://insights.sbomify.com/CVE-2025-38257/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-38257
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-38257
- OSV: https://osv.dev/vulnerability/CVE-2025-38257

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-38257/
Summaries are generated and may contain mistakes; the official description above is the record.