I reproduced with current CURRENT and updated BigID 244962:
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=244962>
$ sysctl -n kern.version
FreeBSD 13.0-CURRENT #0 r359311: Thu Mar 26 04:34:44 UTC 2020
r...@releng1.nyi.freebsd.org:/usr/obj/usr/src/amd64.amd64/sys/GENERIC
$ uname -U
# uname -U
1300084
# pkg info | grep virtualbox
virtualbox-ose-additions-5.2.34_2 VirtualBox additions for FreeBSD guests
# kldload vboxvfs
kldload: an error occurred while loading module vboxvfs. Please check dmesg(8)
for more details.
# dmesg | tail -2
link_elf_obj: symbol bcmp undefined
