/usr/lib/x86_64-linux-gnu/libisofs.so.6 is in libisofs6 1.4.2-2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libisofs.so.6.78.0
/usr/lib/x86_64-linux-gnu/libisofs.so.6.78.0