Windows – Firefox experiences a sec_error_unknown_issuer error for every HTTPS connection

certificatefirefoxhttpswindows 7

When I attempt to connect to any site that uses an HTTPS connection (e.g., I get a 'This Connection is Untrusted' error. I'm using FF 42.0.

I followed the instructions in the The certificate is not trusted because the issuer certificate is unknown section of the "This Connection is Untrusted" error message appears – What to do page–essentially deleting the cert8.db file located in my Firefox profile folder (when FF was closed, BTW).

I restarted FF, but the problem persists.

Chrome (46.0.2490.86 m) and IE (10.0.9200.17519CO) work as expected.

What am I missing?

** edit **

For some reason, the '' option is presented for, so I'm posting the certificate for instead (same error).


general tab


details tab

Best Answer

Looks like you have some bad certificates in your Firefox store. Here is the certificates from and for my browser. You'll see that they are from a trusted certificate authority -- VeriSign and GeoTrust, where yours is from SHC Issuing CA.

The only other thing that might be happening is SSL inspection if your computer is on a corporate network and they have some kind of appliance that does SSL Inspection. But this is unlikely since it works fine with IE and Chrome.

Yahoo Certificate

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Google Certificate

enter image description here

Have a look at this article from Firefox on how to fix the issue.

I would be trying to delete the cert8.db file:

The file cert8.db in your profile folder may have become corrupted. Delete this file while Firefox is closed.

Open your profile folder:

Click the menu button, click help and select Troubleshooting Information. The Troubleshooting Information tab will open.
Under the Application Basics section, click on Show Folder. A window with your profile files will open.
Note: If you are unable to open or use Firefox, follow the instructions in Finding your profile without opening Firefox.

Click the menu button and then click Exit.
Click on the file named cert8.db.
Press Delete.
Restart Firefox.
cert8.db will be recreated when you restart Firefox. This is normal.

Failing that I would be uninstalling and reinstalling Firefox.

Also do a virus scan to check if something bad has infected your browser, just for piece of mind.