What do the security warning codes mean? | Troubleshooting

What do the security warning codes mean?

When Firefox connects to a secure website (the URL begins with "https://"), it must verify that the certificate presented by the website is valid and that the encryption is strong enough to adequately protect your privacy. If the certificate cannot be validated or if the encryption is not strong enough, Firefox will stop the connection to the website and instead, show you an error page with the message, Your connection is not secure:

Fx52InsecureConnection

What to do if you see this error?

If you encounter a "Your connection is not secure" error, you should contact the owners of the website, if possible, and inform them of the error. It is recommended that you wait for the website to be fixed before using it. The safest thing to do is to click Go Back, or to visit a different website. Unless you know and understand the technical reason why the website presented incorrect identification, and are willing to risk communicating over a connection that could be vulnerable to an eavesdropper, you should not proceed to the website.

Technical information

Click on Advanced for more information on why the connection is not secure. Some common errors are described below:

Certificate does not come from a trusted source

The certificate does not come from a trusted source.

Error code: MOZILLA_PKIX_ERROR_ADDITIONAL_POLICY_CONSTRAINT_FAILED

This error indicates that Mozilla's CA Certificate Program has imposed policies upon this website's certificate authority that the website has not complied with. When this error occurs, it indicates that the owners of the website need to work with their certificate authority to correct the policy problem.

Mozilla's CA Certificate Program publishes a list of upcoming policy actions affecting certificate authorities which contains details that might be useful to the website owners. For more information, see the Mozilla Security Blog post, Distrust of Symantec TLS Certificates.

The certificate will not be valid until (date)

The certificate will not be valid until date (...)

Error code: SEC_ERROR_EXPIRED_ISSUER_CERTIFICATE

The error text will also show the current date and time of your system. In case this is incorrect, set your system clock to today's date and time (double-click the clock icon on the Windows Taskbar) in order to fix the problem. More details about this are available in the support article How to troubleshoot time related errors on secure websites.

The certificate expired on (date)

The certificate expired on date (...)

Error code: SEC_ERROR_EXPIRED_CERTIFICATE

This error occurs when a website's identity certification has expired.

The error text will also show the current date and time of your system. In case this is incorrect, set your system clock to today's date and time (double-click the clock icon on the Windows Taskbar) in order to fix the problem. More details about this are available in the support article How to troubleshoot time related errors on secure websites.

The certificate is not trusted because the issuer certificate is unknown

The certificate is not trusted because the issuer certificate is unknown.
The server might not be sending the appropriate intermediate certificates.
An additional root certificate may need to be imported.

Error code: SEC_ERROR_UNKNOWN_ISSUER
The certificate is not trusted because the issuer certificate is unknown.
The server might not be sending the appropriate intermediate certificates.
An additional root certificate may need to be imported.

Error code: MOZILLA_PKIX_ERROR_MITM_DETECTED

MOZILLA_PKIX_ERROR_MITM_DETECTED is a special case of the SEC_ERROR_UNKNOWN_ISSUER error code when a man-in-the-middle attack is detected.

You may have enabled SSL scanning in your security software such as Avast, Bitdefender, ESET or Kaspersky. Try to disable this option. More details are available in the support article How to troubleshoot security error codes on secure websites.

You may also see this error message on major sites like Google, Facebook, YouTube and others on Windows in user accounts protected by Microsoft family settings. To turn these settings off for a particular user, see the Microsoft support article How do I turn off family features?.

The certificate is not trusted because it is self-signed

The certificate is not trusted because it is self-signed.

Error code: ERROR_SELF_SIGNED_CERT

Self-signed certificates make your data safe from eavesdroppers, but say nothing about who the recipient of the data is. This is common for intranet websites that aren't available publicly and you may bypass the warning for such sites. More details are available in the support article How to troubleshoot security error codes on secure websites.

The certificate is only valid for (site name)

example.com uses an invalid security certificate.

The certificate is only valid for the following names: www.example.com, *.example.com

Error code: SSL_ERROR_BAD_CERT_DOMAIN

This error is telling you that the identification sent to you by the site is actually for another site. While anything you send would be safe from eavesdroppers, the recipient may not be who you think it is.

A common situation is when the certificate is actually for a different part of the same site. For example, you may have visited https://example.com, but the certificate is for https://www.example.com. In this case, if you access https://www.example.com directly, you should not receive the warning.

Corrupted certificate store

You may also see certificate error messages when the file in your profile folder that stores your certificates (cert8.dbcert9.db) has become corrupted. Try to delete this file while Firefox is closed to regenerate it:

Note: You should only perform these steps as a last resort, after all other troubleshooting steps have failed.
  1. Open your profile folder:

    Click the menu button New Fx Menu , click help Help-29 Click the menu button Fx57menu , click Help and select Troubleshooting Information. The Troubleshooting Information tab will open.

    • Under the Application Basics section, click on Show FolderOpen FolderShow in FinderOpen Directory. A window will open that contains your profile folder.Your profile folder will open.
    Note: If you are unable to open or use Firefox, follow the instructions in Finding your profile without opening Firefox.

  2. Click the menu button New Fx Menu and then click ExitQuit Close 29 .

    Click the Firefox menu Fx57Menu , then click Exit. Click the Firefox menu at the top of the screen, then click Quit Firefox.Click the Firefox menu Fx57Menu , then click Quit.

  3. Click on the file named cert8.dbcert9.db.
  4. Press command+Delete.
  5. Restart Firefox.
Note: cert8.dbcert9.db will be recreated when you restart Firefox. This is normal.

Bypassing the warning

Note: Some security warnings cannot be bypassed.

You should only bypass the warning if you're confident in both the identity of the website and the integrity of your connection - even if you trust the site, someone could be tampering with your connection. Data you enter into a site over a weakly encrypted connection can be vulnerable to eavesdroppers as well.

In order to bypass the warning page, click Advanced:

  • On sites with a weak encryption you will then be shown an option to load the site using outdated security.
  • On sites which certificate cannot be validated, you might be given the option to add an exception.
Legitimate public sites will not ask you to add an exception for their certificate - in this case an invalid certificate can be an indication of a web page that will defraud you or steal your identity.
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// These fine people helped write this article:AliceWyman, philipp, Tonnes, Goofy, dkeeler, Joni, J.C. Jones. You can help too - find out how.

Last Update: 2018-10-23

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