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How to Fix Error ssl_error_weak_server_ephemeral_dh_key on Mozilla Firefox

In today’s date, Mozilla Firefox is one of the most used browsers, like Google Chrome. If you’re among those who rely on Firefox for most of their internet activity, then there’s a chance you might have faced some techie error messages while trying to visit a website. Some are common ones, and some are unheard and quite difficult to resolve. Among the pool of these errors, one is ssl_error_weak_server_ephemeral_dh_key.

If you’re facing this issue, then hold back, here we’ll give you a step-by-step guide on how to resolve this Mozilla Firefox error message: ssl_error_weak_server_ephemeral_dh_key. But, before we do that, let’s understand what exactly causes this error message.


What’s Firefox ssl_error_weak_server_ephemeral_dh_key Error Message?

This Mozilla Firefox error message ssl_error_weak_server_ephemeral_dh_key is called as the “Diffie Hellman error.” Generally, it occurs when the website you’re visiting has an out-dated security certificate, and some work has needed to be done on it.

Some Other Common Reasons Why This Error Occurs

This error message mostly occurs on those websites that use a self-signed SSL/TLS certificate. That said, due to recent updates, browsers don’t permit the use of a self-signed SSL certificate. Other than that, some of the common causes of this Diffie Hellman error message can be due to:

Bug in Your Installed Mozilla Firefox

It’s quite rare. But if you’re using an out-dated Mozilla Firefox browser, especially the one in which bug was present Firefox 31, then it may cause this error message.

Change in Behaviour of Your Installed Firefox

The Firefox 33 onwards the functionality of libPKIS has been stricter, which does not let anyone disable the library or switch towards NSS code. So, the website you’re visiting can show this error message – ssl_error_weak_server_ephemeral_dh_key.

Key Size Is Not Compatible

Chances are null, but this was one of the reasons once – if the Key size of the security certificate is less than 1024 bits, then it won’t be entertained, and instead, Firefox above 33 will start showing this error message.

Ciphers Being Blocked

If your Mozilla Firefox blocks ciphers, then there’s a high chance that you may end up seeing this Diffie Hellman error message.

Apart from this, some other reasons due to which users can see this error message are:

  • The website you’re visiting is vulnerable to specific online attacks.
  • If the server is Tomcat and there’s no other secure server certificate.
  • Some websites likely keep their servers secured, and to access it, the secured server certificate is required.

A Step-by-step Guide to Fix Error ssl_error_weak_server_ephemeral_dh_key on Mozilla Firefox

Before we jump into the solutions, let’s do some of the basic checks to know whether it resolves the issue or not.

Sometimes it happens that this error is due to the old drivers into your browser. So, first, check and try to update with the latest ones, it may solve the issue. To update the driver,

  • Press Ctrl+Shit+A or
  • Click on Open Menu
  • And, go to Add-ons
Sometimes it has even been claimed that merely refreshing the browser can solve this error message. For refreshing your installed Firefox,

In your Mozilla Firefox menu, (Three Lines at Top Right Side), click “Help Menu.”

Select the option “Troubleshooting Information” from the list of “Help” and click “Refresh Firefox.”
If the issue is persisting, then follow the below solutions.

Substitution of Insecure Fallback Host

To resolve this Mozilla Firefox error message using this solution you need to open the hidden Firefox config menu and have to set the security.tls.insecure_fallback_hosts strings to the domain that’s displayed in error. For doing so, follow the below steps:

Go to your Mozilla Firefox browser and in the address bar type: “about:config”.

Proceed with Caution page will appear over there click on the checkbox “Warn me when I attempt to access these preferences” and then click “Accept the Risk and Continue” button, like below:

As you get to the config menu, paste: “security.tls.insecure_fallback_hosts” in the config menu’s search bar and press enter to get access to this string, which needs to be altered. Like below,
Now, double click on it, the blank Text box will open, in that type the domain name which is showing that error message and then click on the right icon next to it.

Now, restart your Firefox browser and verify whether the website is opening or still shows the same error message, if the error message is still persisting, then move to the next step.

Modifying SSL3 Preferences

It’s suggested to follow the below steps on every installation of Mozilla Firefox, which experience the issue.

Like the above step, again open the hidden config menu of the Mozilla Firefox browser.
1. Copy and paste: “security.ssl3.dhe_rsa_aes_128_sha” and change its preference from true to false.

2. Copy and paste: “security.ssl3.dhe_rsa_aes_256_sha” and change the preference by switching from true to false.


Usually, you won’t come across this Mozilla Error message ssl_error_weak_server_ephemeral_dh_key, but again there’s no surety. If you get this error, simply go through this guide and follow the mentioned steps.

Though some steps like opening a hidden config menu of the web browser may seem a bit new or techie to you, but no need to worry as trying these mentioned solutions won’t harm or change the settings of your browser.

Other SSL Certificate Errors and Troubleshoot Guide

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