I am connecting to a website (via Firefox 6.0.2 on Mac OS X 10.6.8) I know is legitimate, and the connection worked up till yesterday. However, when I connected to day I got the following error:

An error occurred during a connection to [domain].

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)

Is there a way to fix this?

  • If it's a public site I'll take a look - URL?
    – Ram
    Sep 9, 2011 at 18:59
  • Before I could check more, the website started working again. I guess they reissued their certificate? Thanks for everyone's answers.
    – hpy
    Sep 10, 2011 at 3:58

2 Answers 2


If it's a public CA it is likely an operational error which they would very much want to know about. If it's a private CA or cert then the signer should resign it with a new serial number to get rid of the error (bad form to reuse a serial number... unless you are willing to revoke all certs with that # at the same time). You could download the cert (use openssl as an ssl client and have it save the certificate for you) and then explicitly add the certifiate to the FF root store marked as trusted (http://www.mozilla.org/projects/security/pki/nss/tools/certutil.html) but that might not do the trick depending on where NSS is catching the problem. In any case the right action is fixing (re-issuing) the certificate.


It worked before you upgraded Firefox, right? Firefox 6.0.2 was released specifically to address the DigiNotar certificate authority breach by removing suspect CAs from the list of trusted signers. Is your site's certificate one of those?

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