{"id":"CVE-2026-102916","state":"PUBLISHED","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.","publishedAt":"2026-10-09T14:12:08.832Z","updatedAt":"2026-10-09T21:07:26.509Z","severity":{"score":6.8,"label":"Medium","version":"4.0","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","source":"illumos"},"assigner":"illumos","products":["illumos illumos-gate","OmniOS OmniOS"],"affected":[{"vendor":"illumos","product":"illumos-gate","packageName":"system/bhyve","defaultStatus":"affected","versions":[{"version":"e0c0d44e917080841514d0dd031a696c74e8c435","status":"affected","lessThan":"696ecf8debceed9dc33937d8c8e111e4aeebfdae","changes":[{"at":"696ecf8debceed9dc33937d8c8e111e4aeebfdae","status":"unaffected"}],"versionType":"git"}],"platforms":["x86"],"collectionURL":"https://illumos.org","repo":"https://github.com/illumos/illumos-gate","modules":["kernel","bhyve","vmm"],"programFiles":["usr/src/uts/intel/io/vmm/vmm_instruction_emul.c"]},{"vendor":"OmniOS","product":"OmniOS","defaultStatus":"affected","versions":[{"version":"any","status":"affected","lessThan":"r151054","versionType":"custom"},{"version":"r151058","status":"affected","lessThan":"r151058w","changes":[{"at":"r151058w","status":"unaffected"}],"versionType":"custom"},{"version":"r151056","status":"affected","lessThan":"r151056aw","changes":[{"at":"r151056aw","status":"unaffected"}],"versionType":"custom"},{"version":"r151054","status":"affected","lessThan":"r151054bw","changes":[{"at":"r151054bw","status":"unaffected"}],"versionType":"custom"}]}],"references":["https://illumos.topicbox.com/groups/developer/T697a32b688807e56/cve-2026-102916-18491-bhyve-rep-prefix-instr-emulation-fumbles-flags","https://illumos.org/issues/18491","https://github.com/illumos/illumos-gate/commit/696ecf8debceed9dc33937d8c8e111e4aeebfdae","http://www.openwall.com/lists/oss-security/2026/10/09/19"],"weaknesses":["CWE-617"],"ingestedAt":"2026-10-29T20:10:13.529Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/102xxx/CVE-2026-102916.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-102916","state":"PUBLISHED","datePublished":"2026-10-09T14:12:08.832Z","dateUpdated":"2026-10-09T21:07:26.509Z","assignerShortName":"illumos","assignerOrgId":"0ca53633-f0b5-4853-ba72-e0a2e62000d0","dateReserved":"2026-09-29T18:57:32.373Z"},"containers":{"cna":{"title":"Reachable assertion in illumos bhyve REP string instruction emulation allows guest to panic host","descriptions":[{"lang":"en","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."}],"affected":[{"vendor":"illumos","product":"illumos-gate","packageName":"system/bhyve","defaultStatus":"affected","versions":[{"version":"e0c0d44e917080841514d0dd031a696c74e8c435","status":"affected","lessThan":"696ecf8debceed9dc33937d8c8e111e4aeebfdae","changes":[{"at":"696ecf8debceed9dc33937d8c8e111e4aeebfdae","status":"unaffected"}],"versionType":"git"}],"platforms":["x86"],"collectionURL":"https://illumos.org","repo":"https://github.com/illumos/illumos-gate","modules":["kernel","bhyve","vmm"],"programFiles":["usr/src/uts/intel/io/vmm/vmm_instruction_emul.c"]},{"vendor":"OmniOS","product":"OmniOS","defaultStatus":"affected","versions":[{"version":"any","status":"affected","lessThan":"r151054","versionType":"custom"},{"version":"r151058","status":"affected","lessThan":"r151058w","changes":[{"at":"r151058w","status":"unaffected"}],"versionType":"custom"},{"version":"r151056","status":"affected","lessThan":"r151056aw","changes":[{"at":"r151056aw","status":"unaffected"}],"versionType":"custom"},{"version":"r151054","status":"affected","lessThan":"r151054bw","changes":[{"at":"r151054bw","status":"unaffected"}],"versionType":"custom"}]}],"references":[{"url":"https://illumos.topicbox.com/groups/developer/T697a32b688807e56/cve-2026-102916-18491-bhyve-rep-prefix-instr-emulation-fumbles-flags","tags":["mailing-list"]},{"url":"https://illumos.org/issues/18491","tags":["issue-tracking"]},{"url":"https://github.com/illumos/illumos-gate/commit/696ecf8debceed9dc33937d8c8e111e4aeebfdae","tags":["patch"]}],"metrics":[{"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}],"cvssV4_0":{"attackVector":"LOCAL","attackComplexity":"LOW","attackRequirements":"NONE","privilegesRequired":"LOW","userInteraction":"NONE","vulnConfidentialityImpact":"NONE","subConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE","subIntegrityImpact":"NONE","vulnAvailabilityImpact":"HIGH","subAvailabilityImpact":"HIGH","exploitMaturity":"PROOF_OF_CONCEPT","Safety":"NOT_DEFINED","Automatable":"YES","Recovery":"AUTOMATIC","valueDensity":"CONCENTRATED","vulnerabilityResponseEffort":"NOT_DEFINED","providerUrgency":"NOT_DEFINED","version":"4.0","baseSeverity":"MEDIUM","baseScore":6.8,"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"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-617","lang":"en","description":"CWE-617 Reachable Assertion","type":"CWE"}]}],"providerMetadata":{"shortName":"illumos","orgId":"0ca53633-f0b5-4853-ba72-e0a2e62000d0","dateUpdated":"2026-10-09T14:13:38.463Z"},"workarounds":[{"lang":"en","value":"No configuration-level mitigation is available. 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