/usr/lib/x86_64-linux-gnu/libcurl.so.3 is in libcurl3 7.52.1-5+deb9u9.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libcurl.so.4
/usr/lib/x86_64-linux-gnu/libcurl.so.4