# FreeBSD bhyve hypervisor flaws fixed

Published: 2026-10-22 · Severity: routine · Sectors: Technology
Canonical: https://vorant.io/reports/6ca834c7-f3e8-55a0-8dd7-997803f985a8/freebsd-bhyve-hypervisor-flaws-fixed

> Five vulnerabilities in FreeBSD's bhyve hypervisor let a malicious guest VM crash the host or execute code in host userspace; patches available.

NCSC-NL published an advisory covering five vulnerabilities in the FreeBSD bhyve hypervisor, affecting device emulation models including USB 3, HDA audio, and framebuffer. The flaws stem from race conditions, improper validation, and synchronization issues: manipulation of event ring size and Transfer Request Block (TRB) fields in the USB 3 device model, out-of-bounds memory access via improperly checked zero-length Buffer Descriptor List entries in the HDA audio device model, and duplicate/unsynchronized constants plus missing resolution-parameter validation in the framebuffer device model.

A malicious guest virtual machine can exploit these issues to cause denial of service by crashing the bhyve process, or to achieve arbitrary code execution in the host userspace — a serious concern for multi-tenant virtualization environments where guest isolation is a core security boundary. The vulnerabilities are specific to systems running the bhyve hypervisor. FreeBSD has released updates addressing all five CVEs (CVE-2026-101307 through CVE-2026-101311), with CVSS scores ranging from 5.5 to 8.2. No in-the-wild exploitation is reported; this is a vendor-patched disclosure.

Defenders running FreeBSD bhyve should apply the available updates promptly, particularly in environments hosting untrusted or multi-tenant guest VMs, given the potential for guest-to-host escape via code execution.

## Mentioned in this report

- Vulnerabilities: CVE-2026-101307, CVE-2026-101308, CVE-2026-101309, CVE-2026-101310, CVE-2026-101311

Source reporting: https://advisories.ncsc.nl/2026/ncsc-2026-0452.html

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