/usr/lib/x86_64-linux-gnu/libdum.so is in libresiprocate-1.9-dev 1.9.6-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libdum-1.9.so
/usr/lib/x86_64-linux-gnu/libdum-1.9.so