/usr/lib/ruby/vendor_ruby/action_controller/templates/rescues/unknown_action.erb is in ruby-actionpack-2.3 2.3.14-5.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 | <h1>Unknown action</h1>
<p><%=h @exception.message %></p>
|