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.
Advisories

No advisories yet.

Fixes

Solution

Update your illumos distribution to one that includes the fix for this issue.


Workaround

No configuration-level mitigation is available. In-kernel emulation of the local APIC, I/O APIC and HPET cannot be disabled on affected systems. Update to an illumos distribution that includes the fix.

History

Fri, 09 Oct 2026 16:15:00 +0000

Type Values Removed Values Added
First Time appeared Illumos
Illumos illumos-gate
Omnios
Omnios omnios
Vendors & Products Illumos
Illumos illumos-gate
Omnios
Omnios omnios

Fri, 09 Oct 2026 14:30:00 +0000

Type Values Removed Values Added
Description 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.
Title Reachable assertion in illumos bhyve REP string instruction emulation allows guest to panic host
Weaknesses CWE-617
References
Metrics cvssV4_0

{'score': 6.8, 'vector': 'CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H/E:P/AU:Y/R:A/V:C'}


Projects

Sign in to view the affected projects.

cve-icon MITRE

Status: PUBLISHED

Assigner: illumos

Published:

Updated: 2026-10-09T16:46:08.116Z

Reserved: 2026-09-29T18:57:32.373Z

Link: CVE-2026-102916

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-10-09T15:17:06.560

Modified: 2026-10-09T16:35:35.900

Link: CVE-2026-102916

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-10-09T16:00:09Z

Weaknesses