Reachable Assertion Flaw in illumos Bhyve Instruction Emulator Affects Guest VMs

CVE-2026-102916

What is CVE-2026-102916?

A flaw in the illumos Bhyve instruction emulator enables privileged users within guest virtual machines (VMs) to trigger a crash in the host system. When executing REP-prefixed MOVS or STOS instructions targeting Memory-Mapped I/O (MMIO) regions, the emulator fails to clear a status flag on the last iteration. This oversight leads to a failure in the verification process that can result in a denial of service, affecting not only the host but also all other VMs. The issue has been identified since 2020 and impacts all illumos distributions prior to a specific commit that corrects the anomaly.

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