$ vagrant up --provider=aws
Bringing machine 'default' up with 'aws' provider...

An error occurred while executing multiple actions in parallel.
Any errors that occurred are shown below.

An unexpected error ocurred when executing the action on the
'default' machine. Please report this as a bug:

Unable to verify certificate, please set `Excon.defaults[:ssl_ca_path] = path_to_certs`, `ENV['SSL_CERT_DIR'] = path_to_certs`, `Excon.defaults[:ssl_ca_file] = path_to_file`, `ENV['SSL_CERT_FILE'] = path_to_file` or `Excon.defaults[:ssl_verify_peer] = false` (less secure).

C:/Users/DK/.vagrant.d/gems/gems/excon-0.28.0/lib/excon/ssl_socket.rb:76:in `connect'
C:/Users/DK/.vagrant.d/gems/gems/excon-0.28.0/lib/excon/ssl_socket.rb:76:in `initialize'
C:/Users/DK/.vagrant.d/gems/gems/excon-0.28.0/lib/excon/connection.rb:373:in `new'
C:/Users/DK/.vagrant.d/gems/gems/excon-0.28.0/lib/excon/connection.rb:373:in `socket'
C:/Users/DK/.vagrant.d/gems/gems/excon-0.28.0/lib/excon/connection.rb:122:in `request_call'
C:/Users/DK/.vagrant.d/gems/gems/excon-0.28.0/lib/excon/middlewares/mock.rb:42:in `request_ca

対処法

vagrant.bat up --provider=aws