Details

Written by Tech Notes

Published: 26 April 2014

Firefox Fix To No Exception Button Showing When Invalid SSL Certificate Causes
A Secure Connection Failed Message Or A Connection Is Untrusted Message

Please note that I do not get paid to write these articles.

The Problem

When you try to access a website or server or network interface or similar securely via HTTPS in your Internet browser, and you get any of the Images 1 to 3 below or similar, then hopefully the follow solution later helps save you days or weeks of time and resolve the issue for you. 

1. Secure Connection Failed error message by Firefox browser.  Saying it detected an invalid certificate, and that the certificate serial is the same as another it is aware of.
   
   
   
   
2. Secure Connection Failed error message by Firefox browser.  Saying it received a record that exceeded the maximum permissible length.  It is complaining that the authenticity of the received data cannot not be be verified and thus it does not trust it, and is blocking your access.
   
   
   
   
3. A message shows that the "Connection is Untrusted".  It does not like the SSL Certificate and so it does not trust the data, and you are being blocked from accessing the page or site.
   
   
   
   

A few reasons why you can see the above message is if you are trying to access a website with a perfectly good SSL certificate that is either expired, or self generated, or slightly incorrect on the name shown, or it got used on multiple servers or sites, and probably other reasons, which do not make the certificate unusable for the savvy.  Fairly old versions of Firefox have this problem and all the way to the latest versions.  I have seen it on versions before 25, and on 25, and on 28. 

The Fix

The fix I am aware of is the following.

1. I consider this first step as optional because I don't believe it is needed, but it does not hurt to do it, and it is being mentioned because it supposedly helped others. 
   On Firefox, go to History, and clear your history by select Clear Recent History.  You only need to check four boxes and do NOT need to clear and lose your browsing (browser) and download history.
   
   
   
   
2.  On your computers file system, go to where your Firefox profile is.  On a windows OS system, it may be something like, C:\Documents and Settings\Owner\Application Data\Mozilla\Firefox\Profiles\30o8ccgj.default
   
   
3. Exit Firefox (File >> Exit).
   
   
4. Locate the files cert8.db and cert_override.txt, and rename them to cert8.db-Old and cert_override.txt-Old, in case you want to undo what you did. Also, alternatively for the more technical savvy, you can edit the cert_override.txt and remove the specific section related to the site you are trying to access.
   Change this:


To this:
   
   
   
5. Open Firefox, and try accessing the URL via https (secure site).
   
   
6. You are pretty much done! :)  Now you should get something like this image:
   
   
   
   You should see a link or button that says I Understand The Risks, or a similar button or an Exception button or selection.

To No Longer See Such A Warning Message And Get Access To The Secure Site

1.  Click on the "I Understand the Risks" selection or similar, and it should change or take you to a window or page that shows an Exception button or link like this:
   
   
   
   
2. Click on Add Exception, and you will see something like this:
   
   
   
   
   
3. To make the exception permanent so you no longer get asked about the security concern, check the box that says Permanently store this exception, and then click on the OK/Save/Confirm Security Exception button.
   
   
4. You are done.

Related Bug Reports

Here is at least one related Mozilla Bugzilla references, but I saw others too:

Bug 403220
Bug 443972
Bug 659736

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