How To Fix SSL_Error_Bad_Mac_Alert On Firefox

Every browser, including Firefox, has a set SSL and/or TLS Security Protocol to ensure that the websites you visit are safe for browsing. Similarly, all websites must have a valid and relevant SSL security certificate. 

The SSL_Error_Bad_Mac_Alert on Firefox simply means that your browser is having trouble with the verification process of the SSL certificate of websites. It’s common to encounter this error when visiting websites that either don’t have a valid SSL certificate or when the browser has failed to do so. 

Add Website to Insecure FallBack Hosts List

The SSL error usually pops up when Firefox checks the SSL certificate of websites. So, one effective way of fixing this error is by adding the said website to a list called Insecure FallBack Hosts. Adding websites to this list will command Firefox to not monitor the SSL certificate of a specific website. In this way, you won’t regain access to the website.  

However, we suggest proceeding with these steps only if you’re confident about the credibility of the site.

1. Launch Firefox. Click on the address bar and enter about:config. Press Enter.
   
2. After you notice the Proceed with Caution message, select the Accept the Risk and Continue option.  
   
3. On Advanced Preferences, entersecurity.tls.insecure_fallback_hostsin the navigation bar. Now, press Enter and look for the setting preference.
4. Then, click on Edit. 
   
5. Type the specific website’s URL in the new text box and press Enter. 
   
6. Restart Firefox. 

Now, you can check if you’re still having issues with the website. 

Change Transport Layer Security to False

Another common reason the SSL error shows up on Firefox is due to its complications with the TLS 1.3 feature. Also known as 0RTT (Zero Round Trip Time Resumption) data, it can lead to an SSL error due to compatibility issues with Firefox. 

In this method, we’ll change the new TLS security feature to False. Disabling this temporarily can bypass the SSL error. But, it’s important to turn it back on again after your work is done. This is because keeping it disabled will make your browser more vulnerable to security threats.   

1. Type in about:config on the URL address bar. 
2. A Proceed with Caution page will now appear. Proceed by selecting Accept the Risk and Continue. 
3. Enter security.tls.enable_0rtt_data inside the search bar. 
4. Once you see this setting, you’ll see that its status is “True.” Switch the toggle beside it to change it “False.”
   

Turn Off Windows Defender Firewall

The Windows Defender Firewall can sometimes block access to certain websites as it attempts to prevent any malicious threats on your PC. But, it can mistakenly block sites that are not problematic as well. In such scenarios, it’s better to turn off Windows Defender Firewall.

Note: Make sure to turn Defender Firewall back on to keep your PC safe.

1. Open the Start menu and then go to Settings. 
2. Go to the Privacy and Security menu from the left panel and then select Windows Security. If you’re on Windows 10, go to Update and Security and then select Windows Security.
   
3. Navigate to Firewall & Network Protection. 
4. Then, choose a network profile, either Domain network or Private Network, or Public Network. 
   
5. Then, turn off the option below Microsoft Defender Firewall. 
   
6. Do the same for other networks that you’re using. 

Change Date and Time Settings 

Surprisingly, if the date and time setting is incorrect on your PC, the SSL security certificate verification process can fail and may display this error. So, the time on the server and your PC should match to resolve this error. 

1. Press Win + R keys to open Run. 
2. In the text field, typetimedate.cpland then press Enter. Doing so will open your Date and Time settings. 
3. Click on the Change Date and Time settings. 
   
4. Now, set the current date and time. 
5. Then, click on OK and restart your PC.