/usr/lib/mono/4.5/fastcgi-mono-server2.exe.config is in mono-fastcgi-server4 4.2-2.1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/mono/4.5/../gac/fastcgi-mono-server4/3.8.0.0__0738eb9f132ed756/fastcgi-mono-server4.exe.config