CVE-2026-102916

Reachable assertion in illumos bhyve REP string instruction emulation allows guest to panic host

Published Oct 9, 2026 CVSS 4.0 · 6.8 Medium EPSS < 1% KEV · Not listed
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.

Remediation

Vendor Solution

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


Vendor 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.

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

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

Weaknesses

Sources

Status
PUBLISHED
Assigner
illumos
Published
Updated
Oct 9, 2026, 9:07 PM
Reserved
Sep 29, 2026, 6:57 PM
Status
Awaiting Analysis
Published
Oct 9, 2026, 3:17 PM
Modified
Oct 9, 2026, 10:16 PM