/usr/lib/ is in ruby-msgpack 1.1.0-1build2.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/
/usr/lib/ruby/vendor_ruby/
/usr/lib/ruby/vendor_ruby/msgpack/
/usr/lib/ruby/vendor_ruby/msgpack/factory.rb
/usr/lib/ruby/vendor_ruby/msgpack/packer.rb
/usr/lib/ruby/vendor_ruby/msgpack/symbol.rb
/usr/lib/ruby/vendor_ruby/msgpack/unpacker.rb
/usr/lib/ruby/vendor_ruby/msgpack/version.rb
/usr/lib/ruby/vendor_ruby/msgpack.rb
/usr/lib/x86_64-linux-gnu/
/usr/lib/x86_64-linux-gnu/ruby/
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.5.0/
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.5.0/msgpack/
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.5.0/msgpack/msgpack.so