      def instantiate variant, mac=nil
        # Filenames must end in a hex representation of a mac address but only if mac is not empty
        log_halt 403, "Invalid MAC address: #{mac}"                  unless valid_mac?(mac) || mac.nil?
        log_halt 403, "Unrecognized pxeboot config type: #{variant}" unless defined? variant.capitalize
        eval "Proxy::TFTP::#{variant.capitalize}.new"
      end
The software does not restrict or incorrectly restricts access to a resource from an unauthorized actor.