Reachable assertion in illumos bhyve REP string instruction emulation allows guest to panic host
Summary
| CVE | CVE-2026-102916 |
|---|---|
| State | PUBLISHED |
| Assigner | illumos |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-10-09 15:17:06 UTC |
| Updated | 2026-10-09 16:35:35 UTC |
| 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. |
Risk And Classification
Primary CVSS: v4.0 6.8 MEDIUM from 0ca53633-f0b5-4853-ba72-e0a2e62000d0
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/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:Y/R:A/V:C/RE:X/U:X
Problem Types: CWE-617 | CWE-617 CWE-617 Reachable Assertion
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 4.0 | 0ca53633-f0b5-4853-ba72-e0a2e62000d0 | Secondary | 6.8 | MEDIUM | 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/C... |
| 4.0 | CNA | CVSS | 6.8 | MEDIUM | 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/A... |
CVSS v4.0 Breakdown
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/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:Y/R:A/V:C/RE:X/U:X
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Illumos | Illumos-gate | affected e0c0d44e917080841514d0dd031a696c74e8c435 696ecf8debceed9dc33937d8c8e111e4aeebfdae git | x86 |
| CNA | OmniOS | OmniOS | affected any r151054 custom | Not specified |
| CNA | OmniOS | OmniOS | affected r151058 r151058w custom | Not specified |
| CNA | OmniOS | OmniOS | affected r151056 r151056aw custom | Not specified |
| CNA | OmniOS | OmniOS | affected r151054 r151054bw custom | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| illumos.org/issues/18491 | 0ca53633-f0b5-4853-ba72-e0a2e62000d0 | illumos.org | |
| illumos.topicbox.com/groups/developer/T697a32b688807e56/cve-2026-102916-18491-bhyv... | 0ca53633-f0b5-4853-ba72-e0a2e62000d0 | illumos.topicbox.com | |
| github.com/illumos/illumos-gate/commit/696ecf8debceed9dc33937d8c8e111e4a... | 0ca53633-f0b5-4853-ba72-e0a2e62000d0 | github.com | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: iximeow (en)
Additional Advisory Data
Solutions
CNA: Update your illumos distribution to one that includes the fix for this issue.
Workarounds
CNA: 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.