{"id":"CVE-2026-102916","aliases":["EUVD-2026-95796","GHSA-rx9m-cwq2-hf3w"],"status":"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.","severity":{"version":"4.0","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","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-12","score":0.00123,"percentile":0.02125,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-617"],"published":"2026-10-09T14:12:08Z","modified":"2026-11-03T19:06:31Z","products":[{"vendor":"illumos","product":"illumos-gate"},{"vendor":"omnios","product":"omnios"}],"references":[{"url":"https://illumos.topicbox.com/groups/developer/T697a32b688807e56/cve-2026-102916-18491-bhyve-rep-prefix-instr-emulation-fumbles-flags","tags":["mailing-list","article"]},{"url":"https://illumos.org/issues/18491","tags":["issue-tracking","report"]},{"url":"https://github.com/illumos/illumos-gate/commit/696ecf8debceed9dc33937d8c8e111e4aeebfdae","tags":["patch","fix"]},{"url":"http://www.openwall.com/lists/oss-security/2026/10/09/19","tags":["web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-102916","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-rx9m-cwq2-hf3w"},{"url":"https://illumos.org","tags":["web"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/102xxx/CVE-2026-102916.json","tags":["advisory"]},{"url":"https://github.com/illumos/illumos-gate","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2026-102916","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.","status":"published","published":"2026-10-09T14:12:08.832Z","modified":"2026-10-09T21:07:26.509Z","cvss":[{"version":"4.0","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","level":"medium","assessor":"cna"}],"cwes":["CWE-617"],"updated_at":"2026-11-02T13:38:54.394896Z"}],"euvd":[{"id":"EUVD-2026-95796","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.","status":"published","published":"2026-10-09T14:12:08Z","modified":"2026-10-09T21:07:26Z","cvss":[{"version":"4.0","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","level":"medium"}],"updated_at":"2026-11-02T17:27:24.157251Z"}],"ghsa":[{"id":"GHSA-rx9m-cwq2-hf3w","title":"A reachable assertion in the illumos bhyve instruction emulator allows a guest to panic the 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.","status":"published","published":"2026-10-09T15:31:31Z","modified":"2026-10-10T00:31:28Z","cvss":[{"version":"4.0","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/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","level":"medium"}],"cwes":["CWE-617"],"updated_at":"2026-11-02T15:13:01.290603Z"}],"nvd":[{"id":"CVE-2026-102916","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.","status":"published","published":"2026-10-09T15:17:06.56Z","modified":"2026-10-09T22:16:55.22Z","cvss":[{"version":"4.0","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/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","level":"medium","assessor":"secondary"}],"cwes":["CWE-617"],"updated_at":"2026-11-02T14:12:55.473789Z"}],"osv":[{"id":"CVE-2026-102916","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.","status":"published","published":"2026-10-09T14:12:08.832Z","modified":"2026-11-09T13:02:46.063872804Z","cvss":[{"version":"4.0","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","level":"medium"}],"cwes":["CWE-617"],"updated_at":"2026-11-09T03:16:24.800471Z"}]}}