/usr/share/man/man1/vboxcnvt.1.gz is in isdnvboxclient 1:3.25+dfsg1-3.7ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/man/man1/vboxconvert.1.gz
/usr/share/man/man1/vboxconvert.1.gz