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How to Fix SEC_ERROR_REUSED_ISSUER_AND_SERIAL Error Mozilla Firefox?
By Crumb Peter
May 31, 2021
SSL Certificate

How to Fix SEC_ERROR_REUSED_ISSUER_AND_SERIAL Error Mozilla Firefox?

The SEC_ERROR_REUSED_ISSUER_AND_SERIAL error in Mozilla Firefox is a type of SSL (Secure Socket Layer) error that occurs when there is a conflict with the certificate issuer or serial number, typically due to a certificate being reused across multiple sites or certificates that have the same issuer and serial number. This issue prevents you from accessing websites securely, as Firefox refuses to establish a connection with the website.

In this guide, we will explore the causes of this error, and provide detailed solutions to help you fix the SEC_ERROR_REUSED_ISSUER_AND_SERIAL error in Firefox.

What Causes the SEC_ERROR_REUSED_ISSUER_AND_SERIAL Error?

The SEC_ERROR_REUSED_ISSUER_AND_SERIAL error occurs when Firefox detects a situation where two or more SSL certificates from different websites have the same issuer and serial number. In SSL certificates, the issuer is the Certificate Authority (CA) that signed the certificate, and the serial number is a unique identifier assigned to the certificate by the issuer.

When these two parameters are identical for different certificates, Firefox might treat them as potential security risks. This can lead to issues with establishing a secure connection, resulting in the SEC_ERROR_REUSED_ISSUER_AND_SERIAL error.

This issue typically arises in the following scenarios:

  • Misconfigured SSL certificates: A certificate might be issued for multiple domains or reused across different sites.
  • Incorrect certificate installation: A site may have installed an SSL certificate incorrectly or may have multiple certificates with overlapping serial numbers.
  • Outdated or invalid certificates: If an old certificate that is still cached or stored in Firefox’s certificate store is reused by another site, this error can occur.

How to Fix SEC_ERROR_REUSED_ISSUER_AND_SERIAL in Firefox

Here are several methods you can try to resolve the SEC_ERROR_REUSED_ISSUER_AND_SERIAL error in Firefox:

1. Clear SSL Cache and Firefox Certificate Store

A corrupted or outdated SSL cache in Firefox may lead to SSL errors like SEC_ERROR_REUSED_ISSUER_AND_SERIAL. You can try clearing your browser’s SSL state and certificate store to resolve this issue.

Steps to Clear SSL Cache and Certificates:

  1. Clear SSL Cache:
    • Open Firefox.
    • Click on the three horizontal lines in the top-right corner to open the menu.
    • Go to Settings > Privacy & Security.
    • Scroll down to the Cookies and Site Data section.
    • Click Clear Data.
    • Make sure Cached Web Content is checked, and click Clear.
  2. Clear Certificate Store:
    • Open Firefox and click on the three horizontal lines (menu) again.
    • Go to Settings > Privacy & Security.
    • Scroll down to the Certificates section.
    • Click on View Certificates.
    • Under the Authorities tab, review the certificates.
    • If you see any old or duplicate certificates with the same serial number and issuer, you can remove them by selecting and clicking Delete.
    • Restart Firefox.

Once done, check if the error is resolved.

2. Disable SSL Scanning in Antivirus Software

Some antivirus programs scan SSL traffic and may cause conflicts with the SSL certificate, triggering the SEC_ERROR_REUSED_ISSUER_AND_SERIAL error. Disabling SSL scanning in your antivirus software can help fix this issue.

Steps to Disable SSL Scanning in Antivirus Software:

  1. Open your antivirus software.
  2. Locate the SSL or HTTPS scanning settings in the program.
  3. Disable SSL scanning or secure browsing features.
  4. Restart Firefox and try accessing the website again.

If you are unsure how to disable SSL scanning, consult the help documentation of your antivirus software.

3. Check the Website’s SSL Certificate

The issue might not be on your end; it could be due to a problem with the SSL certificate on the website you are trying to visit. You can use SSL checking tools like SSL Labs’ SSL Test to check the status of the SSL certificate for that website.

Steps to Check SSL Certificate:

  1. Go to SSL Labs’ SSL Test.
  2. Enter the website’s domain name (e.g., www.example.com).
  3. Click Submit and wait for the SSL analysis to complete.
  4. Review the results for any issues, such as a reused serial number or a misconfigured certificate.

If the issue is with the website’s SSL certificate, you’ll need to contact the website administrator to have the SSL certificate reissued or properly configured.

4. Update Firefox to the Latest Version

Running an outdated version of Firefox can sometimes lead to compatibility issues with SSL certificates, resulting in errors like SEC_ERROR_REUSED_ISSUER_AND_SERIAL. Ensure you are using the latest version of Firefox to avoid these issues.

Steps to Update Firefox:

  1. Open Firefox.
  2. Click the three horizontal lines in the top-right corner and select Help > About Firefox.
  3. Firefox will automatically check for updates.
  4. If any updates are available, they will be downloaded and installed automatically.
  5. Restart Firefox after updating.

After updating, try accessing the website again to see if the issue is resolved.

5. Check for Conflicting Certificates in Firefox’s Certificate Store

Firefox stores SSL certificates in its certificate store. If there are duplicate or conflicting certificates stored, it could trigger the SEC_ERROR_REUSED_ISSUER_AND_SERIAL error. You can manually inspect and remove problematic certificates.

Steps to Remove Conflicting Certificates:

  1. Open Firefox.
  2. Click on the three horizontal lines (menu) in the top-right corner.
  3. Go to Settings > Privacy & Security.
  4. Scroll down to the Certificates section and click View Certificates.
  5. In the Authorities tab, look for certificates with the same issuer and serial number that may have been duplicated.
  6. Select and click Delete to remove the conflicting certificate(s).
  7. Restart Firefox and check if the error persists.

6. Reset Firefox Settings to Default

If none of the above methods work, you can reset Firefox settings to their default configuration. This will remove any custom settings or modifications that might be causing the issue.

Steps to Reset Firefox:

  1. Open Firefox.
  2. Click on the three horizontal lines (menu) in the top-right corner and select Help > Troubleshooting Information.
  3. Click the Refresh Firefox button.
  4. Confirm the reset, and Firefox will return to its default settings.

This process will remove any add-ons, custom settings, and other configurations, but it should not affect your bookmarks or history.

Conclusion

The SEC_ERROR_REUSED_ISSUER_AND_SERIAL error in Firefox is usually caused by SSL certificate issues, such as certificate reuse, misconfiguration, or duplicate certificates. By following the solutions provided in this guide, such as clearing the SSL cache, checking the website’s SSL certificate, disabling SSL scanning in antivirus software, and updating Firefox, you should be able to fix the error and regain secure access to websites.

If the issue persists, it’s possible that the problem lies with the website’s SSL certificate, in which case the website owner or administrator will need to address the problem.

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Crumb Peter
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    Crumb Peter is a passionate cyber security enthusiast, driven by a constant desire to stay ahead of the curve in this ever-evolving landscape. With an insatiable thirst for knowledge, Crumb actively seeks out and absorbs new advancements in the web and cyber security niche.