In FreeBSD 12.0-STABLE before r350246, 12.0-RELEASE before 12.0-RELEASE-p8, 11.3-STABLE before r350247, 11.3-RELEASE before 11.3-RELEASE-p1, and 11.2-RELEASE before 11.2-RELEASE-p12, the emulated XHCI device included with the bhyve hypervisor did not properly validate data provided by the guest, allowing an out-of-bounds read. This provides a malicious guest the possibility to crash the system or access system memory.
https://security.netapp.com/advisory/ntap-20190814-0003/
https://security.FreeBSD.org/advisories/FreeBSD-SA-19:16.bhyve.asc
http://packetstormsecurity.com/files/153753/FreeBSD-Security-Advisory-FreeBSD-SA-19-16.bhyve.html