{"api_version":"1","generated_at":"2026-10-09T16:53:05+00:00","cve":"CVE-2026-102916","urls":{"html":"https://cve.report/CVE-2026-102916","api":"https://cve.report/api/cve/CVE-2026-102916.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-102916","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-102916"},"summary":{"title":"Reachable assertion in illumos bhyve REP string instruction emulation allows guest to panic host","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.","state":"PUBLISHED","assigner":"illumos","published_at":"2026-10-09 15:17:06","updated_at":"2026-10-09 16:35:35"},"problem_types":["CWE-617","CWE-617 CWE-617 Reachable 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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."}],"value":"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."}],"metrics":[{"cvssV4_0":{"Automatable":"YES","Recovery":"AUTOMATIC","Safety":"NOT_DEFINED","attackComplexity":"LOW","attackRequirements":"NONE","attackVector":"LOCAL","baseScore":6.8,"baseSeverity":"MEDIUM","exploitMaturity":"PROOF_OF_CONCEPT","privilegesRequired":"LOW","providerUrgency":"NOT_DEFINED","subAvailabilityImpact":"HIGH","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","userInteraction":"NONE","valueDensity":"CONCENTRATED","vectorString":"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","version":"4.0","vulnAvailabilityImpact":"HIGH","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE","vulnerabilityResponseEffort":"NOT_DEFINED"},"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}]}],"problemTypes":[{"descriptions":[{"cweId":"CWE-617","description":"CWE-617 Reachable Assertion","lang":"en","type":"CWE"}]}],"providerMetadata":{"dateUpdated":"2026-10-09T14:13:38.463Z","orgId":"0ca53633-f0b5-4853-ba72-e0a2e62000d0","shortName":"illumos"},"references":[{"tags":["mailing-list"],"url":"https://illumos.topicbox.com/groups/developer/T697a32b688807e56/cve-2026-102916-18491-bhyve-rep-prefix-instr-emulation-fumbles-flags"},{"tags":["issue-tracking"],"url":"https://illumos.org/issues/18491"},{"tags":["patch"],"url":"https://github.com/illumos/illumos-gate/commit/696ecf8debceed9dc33937d8c8e111e4aeebfdae"}],"solutions":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"Update your illumos distribution to one that includes the fix for this issue."}],"value":"Update your illumos distribution to one that includes the fix for this issue."}],"source":{"discovery":"INTERNAL"},"title":"Reachable assertion in illumos bhyve REP string instruction emulation allows guest to panic host","workarounds":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"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."}],"value":"No configuration-level mitigation is available. In-kernel emulation of the local APIC, I/O APIC and HPET cannot be disabled on affected systems. 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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.","Type":"Description","Title":"Reachable assertion in illumos bhyve REP string instruction emul"}]}}}