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The workaround in the article "Certificate contains the same serial number as another certificate" did not work for me, any more ideas?


Have reinstalled the open source 'Endian Firewall' on another machine, which is accessed using a browser using HTTPS. It does not have valid certificates but I have always been able to add an override however, this time I can not. The workaround provided in the Firefox support area mentioned above does not solve the problem. I urgently need to access the firewall to make some config changes but have reached a dead end. The article says it may be out of date, is there another workaround I can try? Will reinstalling the firewall or reinstalling Firefox reset the old behaviour?

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  • User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:17.0) Gecko/17.0 Firefox/17.0

More Information

Error Message:
Secure Connection Failed
An error occurred during a connection to XXX.
You have received an invalid certificate. Please contact the server administrator or email correspondent and give them the following information:
Your certificate contains the same serial number as another certificate issued by the certificate authority. Please get a new certificate containing a unique serial number.
(Error code: sec_error_reused_issuer_and_serial)
Other software is Endian Firewall 2.5.1
On previous occasions when I have updated Endian, Firefox has provided a dilog box that allows me to create an exception - but not this time.

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Helpful Reply

hello bonoky,can you try the following: go to firefox > help > troubleshooting information and open the profile directory (then close firefox). in the profile folder rename the files cert_override.txt & cert8.db to something like oldcert... & launch firefox again.

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2368 solutions 20966 answers

Helpful Reply

I don't think Firefox would know about the duplicate number unless it is still saved in Firefox's certificate file. If you followed the steps in the article (Certificate contains the same serial number as another certificate) to delete any previously saved "fake" certificate, you might need to restart Firefox before trying to save the new one.

If restarting Firefox doesn't help, you could try creating a new Firefox profile, which will have clean settings files and a blank cache. This article has the steps for creating and switching between profiles. Please take care not to delete any profiles unless/until you are 110% sure that you will never need any of the data in them.

Use the Profile Manager to create and remove Firefox profiles

Whether that helps or not, you can always switch back to your regular profile for normal browsing.

Question owner

Thanks for your responses.

Investigating the route suggested by the official workaround, I discoverd that as well as the two items suggested, there was a third entry in the "Servers" section associated with the server on which the software was installed that needed to be deleted. Once I did this it provide the old warning box that enabled me to create an override.

Problem solved