/usr/lib/mono/4.0/fastcgi-mono-server4.exe is in mono-fastcgi-server4 2.10-1build1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/mono/4.0/../gac/fastcgi-mono-server4/2.10.0.0__0738eb9f132ed756/fastcgi-mono-server4.exe