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How to fix SSL_error_bad_mac_alert?

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  • 4 min read

Firefox is one of the most popular browsers in the world. However, as popular as it is, it isn’t immune to random bugs, glitches and configuration issues which can sometimes cause users to lose access to specific websites. 

In this article, we’re talking about the “SSL_error_bad_mac_alert” error in Firefox, its causes and what you can do to fix the problem. 

What causes this error?

The error is generally caused by a failed SSL handshake causing the browser to think that the site you’re trying to visit isn’t secure. Other possible causes include:

  • Aggressive firewall settings. 
  • Internet connectivity issues.
  • ISP blocking.
  • Invalid SSL certificate on the target site. 
  • Incorrect date and time settings on your machine. 
  • SSL3 server settings aren’t enabled. 

Also read: How to fix SSL syscall error: eof detected?

How to fix this?

Here are six fixes you can try out. 

Restart your router

Power cycling your network equipment is the fix to more issues than you think. More often than not, connectivity issues can be caused by an underlying bug in your router and can be fixed by rebooting.

Check the firewall

Sometimes the Windows Firewall can get in the way of programs trying to access the internet, which can very well be the case here. Try temporarily disabling your firewall to see if Firefox starts working properly.

You can check out how to use the Windows Firewall here

Check your date and time settings

Another potential cause of the error can be incorrect date and time settings on your PC. If your local machine’s time isn’t set correctly, you can run into a lot of issues on the internet and might not be able to visit any sites at all. 

Check out our detailed guide on how to fix the date and time settings on your PC here. 

Add the site to the insecure fallbacks list

If you trust the website you’re visiting to be secure, you can add its URL to the insecure fallbacks list which tells Firefox to not look for an SSL certificate on a particular site. Here’s how.

Step 1: Open Firefox and type about:config in the URL bar. Once the page loads, type in security.tls.insecure_fallback_hosts in the search bar to bring up the list and click the edit icon in the far right. 

Step 2: Enter the website’s URL and hit enter. 

Restart Firefox and the error should be gone. 

Check SSL and TLS protocols

Firefox not enabling the SSL3 and TSL1 protocols by default can also cause this error as the browser would then not be able to recognise older certificates. Here’s how you can enable them,

Step 1: Open Firefox and type about:config in the URL bar. Hit enter to proceed.

Step 2: Once the page loads, type in security.ssl3 in the search bar to bring up all SSL3-related configurations. Ensure that the settings are set to true. 

Now restart Firefox and the error should be gone. 

Bypass Firefox encryption protocols

Finally, you can bypass Firefox’s encryption protocols to get to the site you want. Do remember that it’s not recommended to do this as it’ll open you to risks from unknown and potentially malicious websites. 

All you have to do is open Firefox and head to about:preferences#privacyOnce on the page, uncheck the Block dangerous and deceptive content setting under Security. 

Also read: How to fix SSL_Error_No_Cypher_Overlap?

Yadullah Abidi

Yadullah Abidi

Yadullah is a Computer Science graduate who writes/edits/shoots/codes all things cybersecurity, gaming, and tech hardware. When he's not, he streams himself racing virtual cars. He's been writing and reporting on tech and cybersecurity with websites like Candid.Technology and MakeUseOf since 2018. You can contact him here: