---
id: CVE-2025-40102
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  KVM: arm64: Prevent access to vCPU events before init

  Another day, another syzkaller bug
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  KVM: arm64: Prevent access to vCPU events before init

  Another day, another syzkaller bug. KVM erroneously allows userspace to
  pend vCPU events for a vCPU that hasn't b…
severity: none
published: '2025-10-30'
updated: '2026-09-02'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-40102'
references:
  - url: 'https://git.kernel.org/stable/c/0aa1b76fe1429629215a7c79820e4b96233ac4a3'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/64a04e6320fc5affbadc59dc7024d79f909bfe84'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/7b854e68365a84dfa984ee81268e10b9311ac9d2'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/b0ab34a9e4cd5b88b522cc156e792cefe3085334'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/b498f0da45a388b40195f7198455c62fe366a372'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/c0fcd72e7eb50205dc20731033b0b1c67ecbe4dc'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/d64461d38972302f0243498ff409b0d54e14e106'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
epss: 0.00207
epssPercentile: 0.09575
ingestedAt: '2026-09-02T13:44:41.173Z'
---

## Overview

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

KVM: arm64: Prevent access to vCPU events before init

Another day, another syzkaller bug. KVM erroneously allows userspace to
pend vCPU events for a vCPU that hasn't been initialized yet, leading to
KVM interpreting a bunch of uninitialized garbage for routing /
injecting the exception.

In one case the injection code and the hyp disagree on whether the vCPU
has a 32bit EL1 and put the vCPU into an illegal mode for AArch64,
tripping the BUG() in exception_target_el() during the next injection:

  kernel BUG at arch/arm64/kvm/inject_fault.c:40!
  Internal error: Oops - BUG: 00000000f2000800 [#1]  SMP
  CPU: 3 UID: 0 PID: 318 Comm: repro Not tainted 6.17.0-rc4-00104-g10fd0285305d #6 PREEMPT
  Hardware name: linux,dummy-virt (DT)
  pstate: 21402009 (nzCv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--)
  pc : exception_target_el+0x88/0x8c
  lr : pend_serror_exception+0x18/0x13c
  sp : ffff800082f03a10
  x29: ffff800082f03a10 x28: ffff0000cb132280 x27: 0000000000000000
  x26: 0000000000000000 x25: ffff0000c2a99c20 x24: 0000000000000000
  x23: 0000000000008000 x22: 0000000000000002 x21: 0000000000000004
  x20: 0000000000008000 x19: ffff0000c2a99c20 x18: 0000000000000000
  x17: 0000000000000000 x16: 0000000000000000 x15: 00000000200000c0
  x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000
  x11: 0000000000000000 x10: 0000000000000000 x9 : 0000000000000000
  x8 : ffff800082f03af8 x7 : 0000000000000000 x6 : 0000000000000000
  x5 : ffff800080f621f0 x4 : 0000000000000000 x3 : 0000000000000000
  x2 : 000000000040009b x1 : 0000000000000003 x0 : ffff0000c2a99c20
  Call trace:
   exception_target_el+0x88/0x8c (P)
   kvm_inject_serror_esr+0x40/0x3b4
   __kvm_arm_vcpu_set_events+0xf0/0x100
   kvm_arch_vcpu_ioctl+0x180/0x9d4
   kvm_vcpu_ioctl+0x60c/0x9f4
   __arm64_sys_ioctl+0xac/0x104
   invoke_syscall+0x48/0x110
   el0_svc_common.constprop.0+0x40/0xe0
   do_el0_svc+0x1c/0x28
   el0_svc+0x34/0xf0
   el0t_64_sync_handler+0xa0/0xe4
   el0t_64_sync+0x198/0x19c
  Code: f946bc01 b4fffe61 9101e020 17fffff2 (d4210000)

Reject the ioctls outright as no sane VMM would call these before
KVM_ARM_VCPU_INIT anyway. Even if it did the exception would've been
thrown away by the eventual reset of the vCPU's state.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.