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Firefox and weak ephemeral Diffie-Hellman key

You can work around the Firefox browser security warning “SSL received a weak ephemeral Diffie-Hellman key in Server Key Exchange handshake message. (Error code: ssl_error_weak_server_ephemeral_dh_key)” by referring to this Mozilla Q&A post:


The short version:

Workaround for Firefox 39 and above:

  1. In FireFox, enter “about:config” in the URL field and press enter
  2. Accept the “This might void your warranty!” warning
  3. In the search field at the top, enter “security.ssl3.dhe_rsa_aes
  4. Double click each result (128 and 256) to toggle the Value to “false

Now retry your site – it should work now. Remember to change these settings back when you’re done.