Have a question regarding weak ephemeral Diffie-Hellman key in Server Key Exchange handshake message.

Hopefully this is an easy fix as I don't truly understand ciphers etc...

We have a spam filter (Websense).  Our users get emailed a link daily allowing them to see what spam they have.  If they use Firefox they get an error message with the following:

An error occurred during a connection to c*****:8443. SSL received a weak ephemeral Diffie-Hellman key in Server Key Exchange handshake message. (Error code: ssl_error_weak_server_ephemeral_dh_key)

    The page you are trying to view cannot be shown because the authenticity of the received data could not be verified.
    Please contact the website owners to inform them of this problem.

Is the issue on the server end or in Firefox?  I've installed IIS Crypto on the Server so I can see protocols, ciphers, cipher suites, Hashes Key Exchanges etc but am unsure on what to do.  I also have seen the work around where you can go into the config of Firefox and change some setting to false to bypass some of the security settings but this doesn't seem like a practical solution.

Ideas or help?

fwiw users with Chrome get a similar message but IE and Opera users can connect fine?

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Sean JacksonInformation Security AnalystCommented:
I'm not 100% sure, but make sure all the browsers are up dated to the current version, and make sure the server has these ciphers enabled:

The cause is that you are using ciphers on the server side that the latest versions of Firefox and Chrome have deprecated.  So you can either change the setting on the Firefox side to allow the use of the cipher(s), or change the server side to not use those.

If I remember right, the settings for Firefox are

So if you disable those on the server side you should be good.  I think those would equate to

If the server is accessible via the internet, I would advise checking it against https://www.ssllabs.com/ssltest/

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BlueGooseAuthor Commented:
It ended up being an issue on the server side.  My vendor needed to load a new xml file that was compatible with the new security that Firefox has in it's latest update
BlueGooseAuthor Commented:
I've requested that this question be closed as follows:

Accepted answer: 0 points for BlueGoose's comment #a40997706

for the following reason:

Ended up being a server side issue and nothing to do with the browser
BlueGooseAuthor Commented:
Assigning points as you did mention in your answer that the issue may lie on the server side
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Microsoft IIS Web Server

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