---
id: CVE-2026-102916
title: >-
  A reachable assertion in the illumos bhyve instruction emulator allows a guest
  to panic the host
summary: >-
  A reachable assertion in the illumos bhyve instruction emulator allows a guest
  to panic the host. When emulating a REP-prefixed MOVS or STOS instruction that
  accesses guest MMIO, vie_emulate_movs() and vie_emulate_stos() in
  usr/src/uts/i…
severity: none
cwe:
  - CWE-617
published: '2026-10-09'
updated: '2026-10-09'
sourceUpdated: '2026-10-09T17:16:43.520'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-102916'
references:
  - url: >-
      https://github.com/illumos/illumos-gate/commit/696ecf8debceed9dc33937d8c8e111e4aeebfdae
    label: 0ca53633-f0b5-4853-ba72-e0a2e62000d0
  - url: 'https://illumos.org/issues/18491'
    label: 0ca53633-f0b5-4853-ba72-e0a2e62000d0
  - url: >-
      https://illumos.topicbox.com/groups/developer/T697a32b688807e56/cve-2026-102916-18491-bhyve-rep-prefix-instr-emulation-fumbles-flags
    label: 0ca53633-f0b5-4853-ba72-e0a2e62000d0
tags:
  - nvd
ingestedAt: '2026-10-09T16:02:33.373Z'
---

## Overview

A reachable assertion in the illumos bhyve instruction emulator allows a guest to panic the host. When emulating a REP-prefixed MOVS or STOS instruction that accesses guest MMIO, vie_emulate_movs() and vie_emulate_stos() in usr/src/uts/intel/io/vmm/vmm_instruction_emul.c do not clear the VIES_REPEAT status flag on the final iteration. For MMIO regions emulated in the kernel (the local APIC, I/O APIC and HPET), the stale flag causes a VERIFY assertion in vie_advance_pc() to fail, and the host panics. A privileged user within a guest VM can issue a REP MOVS or REP STOS instruction against the local APIC page to cause a denial of service of the host and every other guest running on it. The flaw has existed since 2020 (illumos-gate commit e0c0d44e), and affects any illumos distribution prior to illumos-gate commit 696ecf8d.

## Remediation

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