How To Fix the MOZILLA_PKIX_ERROR_OCSP_RESPONSE_FOR_CERT_MISSING Error

While it may not be as popular as Chrome, Mozilla Firefox is still one of the most powerful browsers on the market. However, you may still encounter some problems while using it. These include SSL issues like the MOZILLA_PKIX_ERROR_OCSP_RESPONSE_FOR_CERT_MISSING error, which prevents you from accessing a website.

Fortunately, this error is quite easy to fix. You may simply need to restart Mozilla or configure a few settings in the browser.

In this post, we’ll look closely at the MOZILLA_PKIX_ERROR_OCSP_RESPONSE_FOR_CERT_MISSING error and what it means. Then, we’ll show you how to fix it. Let’s get started!

What Is the MOZILLA_PKIX_ERROR_OCSP_RESPONSE_FOR_CERT_MISSING Error?

“MOZILLA_PKIX_ERROR_OCSP_RESPONSE_FOR_CERT_MISSING” is an error message that can appear when you’re trying to access a website using Mozilla Firefox. It typically means that the site has a missing or invalid Secure Sockets Layer (SSL) certificate.

However, the message can display on your browser even if the website has a valid SSL certificate. For example, there may be a connectivity issue or a glitch with OCSP stapling.

What Is OCSP?

Online Certificate Status Protocol (OCSP) enables browsers to verify if a website’s SSL or TLS certificate has been revoked. If a website cannot provide a valid OCSP response, you may see the MOZILLA_PKIX_ERROR_OCSP_RESPONSE_FOR_CERT_MISSING error. Before we take a closer look at OCSP, let’s briefly cover how SSL works.

SSL certificates provide secure connections between browsers and websites. They encrypt this communication to prevent sensitive information such as passwords and credit card numbers from being intercepted by malicious third parties.

SSL certificates are issued by Certificate Authorities (CAs). These trusted organizations can verify the identity of the website owner and the authenticity of the website:

There are different types of SSL certificates available, some of them providing a higher level of security for sites that handle sensitive information. Installing an SSL certificate is one of the first things you’ll need to do when setting up a website. However, many trusted hosting providers will do it for you.

Now, let’s get back to OCSP. As mentioned earlier, this protocol checks an SSL certificate’s revocation status. Sometimes, a website is unable to provide a valid OCSP response to the browser. As a result, the browser cannot determine the site’s revocation status, resulting in the MOZILLA_PKIX_ERROR_OCSP_RESPONSE_FOR_CERT_MISSING error.

This error can be caused by several factors, including:

• A misconfigured OCSP server
• Network issues that prevent the browser from connecting to the OCSP server
• The OCSP server is down or offline

Another cause could be a misconfigured SSL certificate. For example, the certificate might not include the information needed to retrieve the OCSP response. Additionally, you could also be dealing with an OCSP stapling issue.

What Is OCSP Stapling in Mozilla Firefox?

When they encounter an SSL certificate, browsers connect to the CA to verify its status.

OCSP stapling is a feature that eliminates the need for the browser to query CA servers. It’s used by various browsers, including Mozilla Firefox.

When OCSP stapling is enabled, the website makes periodic requests to the CA and retrieves “signed proof” of the certificate’s validity. It can then provide a cached OCSP response to the browser.

Since the browser doesn’t need to communicate with the OCSP server, the stapling feature can help improve loading times and a site’s overall performance. It can also reduce the risk of “man-in-the-middle” attacks and provide more security.

With OCSP stapling, the browser can decide whether to terminate the secure connection for invalid certificates. However, an issue with this feature may cause Firefox to falsely identify an SSL certificate as invalid.

How To Fix the MOZILLA_PKIX_ERROR_OCSP_RESPONSE_FOR_CERT_MISSING Error (3 Methods)

Before you try fixing the MOZILLA_PKIX_ERROR_OCSP_RESPONSE_FOR_CERT_MISSING error, we recommend accessing the same website from a different browser. If you receive a similar SSL error, then it’s likely that the site has an invalid certificate.

If the website in question is yours, you’ll need to see if your SSL certificate has been revoked (and why). You can do this by contacting the CA that issued your certificate. If the certificate is included in your hosting plan, you can reach out to your web host instead.

However, if you’re only encountering this error in Firefox, there might be a problem with the browser. Fortunately, this is easy to solve. Let’s look at a few possible fixes!

1. Restart or Reinstall Firefox

Sometimes, the MOZILLA_PKIX_ERROR_OCSP_RESPONSE_FOR_CERT_MISSING error is a temporary glitch. Therefore, it’s worth restarting or reinstalling Firefox.

To restart Firefox, simply type “about:profiles” into the search bar and hit Enter. Then, on the page, locate the Restart box and click on Restart normally:

You can also check to see if you’re running the most recent browser version. Click on the hamburger icon in the top-right corner of the browser and select Settings.

Under General, look for the Firefox Updates section:

Here, you can see if your browser is up to date or needs updating. You might also want to make sure that you have automatic updates enabled to prevent technical issues in the future.

Now, try accessing the website again. You can move on to the next method if you’re still encountering issues.

2. Clear the Cache

Sometimes, outdated cached data could lead to SSL errors. Your browser stores data about the websites you visit. This way, it can serve this cached information on your next visit and improve the user experience by speeding up the page loading times.

However, if Firefox is serving data that is no longer valid, it may lead to the MOZILLA_PKIX_ERROR_OCSP_RESPONSE_FOR_CERT_MISSING error. To check whether this is the case, you’ll need to clear the cache.

In Firefox, click on the hamburger icon again and select Settings. Then, go to Privacy & Security and locate the Cookies & Site Data section:

Click on the Clear Data button. In the popup window, make sure that the box for Cached Web Content is ticked and hit Clear:

Note that if you select Cookies and Site Data, you’ll be signed out of all websites. This isn’t necessary for troubleshooting the MOZILLA_PKIX_ERROR_OCSP_RESPONSE_FOR_CERT_MISSING error — you only need to clear the cached data!

3. Disable Browser Extensions

If you’ve restarted Firefox and cleared the cache but you’re still seeing the MOZILLA_PKIX_ERROR_OCSP_RESPONSE_FOR_CERT_MISSING error, it’s time to try disabling your browser extensions. In some cases, glitchy third-party software may trigger SSL errors.

To disable extensions in Firefox, click on the hamburger icon and select Add-ons and themes. Then, go to Extensions and use the toggle switch to disable them:

After disabling an extension, you’ll need to refresh the website that’s producing the MOZILLA_PKIX_ERROR_OCSP_RESPONSE_FOR_CERT_MISSING error. This will help you identify the culprit.

Don’t worry if you still encounter the error after disabling your extensions. There’s still one more troubleshooting method that you can try!

4. Disable OCSP Stapling

As we mentioned above, the MOZILLA_PKIX_ERROR_OCSP_RESPONSE_FOR_CERT_MISSING error could also be caused by an issue with the OCSP stapling feature. Therefore, you may need to disable it.

Open Firefox and type “about:config” into the search bar. This will give you a warning:

Click on Accept the Risk and Continue. On the next page, enter “enable_ocsp” into the search box, and you’ll get the following two results:

To disable OCSP stapling, all you have to do is double-click on each of the two options. This will automatically change their values to false:

Now, try accessing the website again. If you decide to enable OCSP stapling again, you’ll just need to double-click on those options and change their values back to true.

Summary

The MOZILLA_PKIX_ERROR_OCSP_RESPONSE_FOR_CERT_MISSING error happens when the website you’re trying to visit fails to provide a valid OCSP response. This is usually because there’s a problem with the OCSP server or a connectivity issue.

To solve the problem, try restarting or reinstalling Mozilla Firefox and clearing the browser cache. If that doesn’t work, it’s time to disable your browser extensions and OCSP stapling.

Using a reliable hosting provider for your website can help prevent SSL issues and other errors. At Kinsta, all of our plans come with top-notch security and performance features to keep your site running smoothly. Plus, if you do run into any problems, we offer expert support 24/7. Check out our managed WordPress hosting plans today!