/usr/lib/x86_64-linux-gnu/libestbase.so is in libestools2.1-dev 1:2.1~release-6.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libestbase.so.2.1
/usr/lib/x86_64-linux-gnu/libestbase.so.2.1