---
id: "CVE-2026-98470"
kind: "vulnerability"
aliases: ["CVE-2026-98470"]
title: "Linux KVM on arm64: unknown VM ioctl triggers kernel WARN, panics pKVM hosts"
severity: "low"
cvss: null
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["arm64", "kvm", "linux-kernel", "pkvm", "runtime"]
not_affected_if: ["non-pkvm", "panic-on-warn-disabled", "x86-host"]
published_at: "2026-10-18T16:16:57+00:00"
first_seen_at: "2026-10-23T21:57:15+00:00"
updated_at: "2026-10-25T05:26:02+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98470", "first_seen_at": "2026-10-23T21:57:15+00:00"}]
---

# Linux KVM on arm64: unknown VM ioctl triggers kernel WARN, panics pKVM hosts

On arm64 Linux hosts running in protected KVM (pKVM) mode, an unrecognized VM ioctl from userspace makes the kernel emit a WARN, which taints the host and panics it when panic_on_warn is set. The result is a denial of service by a local user who can issue ioctls on a VM file descriptor, not code execution.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- unknown

## Fix

- Update to a Linux kernel release that includes the upstream commit resolving this CVE (fixed version not stated in the source)
- Until patched, leave `panic_on_warn` at `0` on pKVM hosts

## Timeline

- 2026-10-23T21:57:15+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-98470

## From the sources

In the Linux kernel, the following vulnerability has been resolved:

KVM: arm64: Don't WARN on an unknown VM ioctl in protected mode

kvm_pkvm_ioctl_allowed() WARNs when kvm_get_cap_for_kvm_ioctl() doesn't
find the ioctl number in vm_ioctl_caps[], and kvm_arch_vm_ioctl() calls
it for every number the generic code doesn't handle, so
ioctl(vm_fd, 0xdeadbeef) from userspace taints a pKVM host and panics it
under panic_on_warn. The lookup is fed userspace input: return false,
and userspace gets the -EINVAL kvm_arch_vm_ioctl() returns for that
number on a host without pKVM.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_