/usr/lib/x86_64-linux-gnu/libdum.so is in libresiprocate-1.11-dev 1:1.11.0~beta5-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libdum-1.11.so
/usr/lib/x86_64-linux-gnu/libdum-1.11.so