Currently experiencing an “SSL_ERROR_NO_CYPHER_OVERLAP” error code in the Mozilla Firefox web browser?

You’ve come to the right place – in this guide, we’ll show you exactly how to fix it. 


The “SSL_ERROR_NO_CYPHER_OVERLAP” error occurs when your browser is unable to obtain the security data for a website you’re trying to access. Unlike other browser errors, the SSL_ERROR_NO_CYPHER_OVERLAP error happens specifically with Firefox. Google Chrome has a similar but slightly different version of it, with its message reading “ERR_SSL_VERSION_OR_CIPHER_MISMATCH“.


SSL stands for Secure Sockets Layer and is responsible for providing privacy, authentication, and integrity to internet communications. The “SSL_ERROR_NO_CYPHER_OVERLAP” error typically occurs when Firefox fails to get the proper security information from the website your browser is attempting to establish a connection with. This can happen for a variety of reasons… 

What Causes the SSL_ERROR_NO_CYPHER_OVERLAP Error in Firefox?

It may be due to the website itself (something server-side) or a locally misconfigured setting in your Firefox browser. If many different websites give you the same error, it is far more likely to be your own Firefox browser settings. 

An outdated version of Firefox is also a potential cause of Firefox error “SSL_ERROR_NO_CYPHER_OVERLAP” appearing. In any case, it’s best to always keep Firefox up-to-date to avoid errors like this in the future.


Coming across errors is never a great experience, and we try our best to make it a learning one. With each problem, there’s bound to be a solution. The “SSL_ERROR_NO_CYPHER_OVERLAP” error is no exception. 

So, without further ado, let’s dive right in and fix this error…

1. Update Firefox Browser

Update your Firefox Web Browser. An outdated Firefox version is prone to the “SSL_ERROR_NO_CYPHER_OVERLAP” error appearing This is because older Firefox versions might support outdated cypher suites and obsolete TLS versions, which are kept up-to-date for a reason. 

Installing the latest update for your Firefox web browser is a fairly simple task.

To update Firefox – open your browser, and:

  1. Select the Menu button at the top-right corner of your screen. This is the icon with three lines. 
  2. Click Help and select About Firefox.
  3. The About Mozilla Firefox window opens. Firefox will check for updates and download them automatically.
  1. When the download is complete, select Restart to update Firefox.
screenshot of firefox updating

Note: As mentioned in the official Firefox support website, if you had any problems with updating, simply download the latest version of Firefox. You can do so by heading to the Systems & Languages page or you can also use their official download page.

2. Reset SSL3 and TLS Settings

If you’re already using the latest version of Firefox or updating didn’t help, the next step is resetting your SSL3 and TLS settings. Not all websites require these protocols to make a connection, but some do. Therefore, if these settings in your Firefox browser are disabled, it might be the reason you’re running into the “SSL_ERROR_NO_CYPHER_OVERLAP” error.

To reset your SSL3 & TLS Settings: 

  1. Open a new tab in your Firefox browser and type “about:config” in the address bar. You may see a message saying, “This might void your warranty!” or “Proceed with Caution”. 

This warning is Firefox’s way of preventing users, such as yourself, from accidentally making critical changes to your browser’s settings. But we know what we’re doing, so click on Accept the Risk and Continue to proceed.

  1. The “Advanced Preferences” screen should appear. In the search bar, type “tls”. 
advanced preferences error code solution

This generates the list of all your TLS configurations.

  1. Values that are bolded indicate that they have been changed. Right-click on them and select Reset to restore them to the default settings.
  2. Afterward, repeat the same process for SSL3. Type “ssl3” in the search bar, and reset any changed value.
how to fix error code SSL_ERROR_NO_CYPHER_OVERLAP

Additionally, make sure that the following two items are set to false.

  • security.ssl3.dhe_rsa_aes_128_sha
  • security.ssl3.dhe_rsa_aes_256_sha

Setting these to false disables Firefox from using these low-encryption cyphers. This is essential for security purposes.

3. Bypass Security Protocols and Configurations of Your Browser

It’s generally not recommended to bypass browser security protocols as their job is to keep you from accessing unsafe websites. That being said, if you know the site you’re trying to access is secure, manually entering a cypher validation should help bypass this error.

To bypass browser security protocols:

  1. Navigate again to the “about:config” screen of your Firefox browser and type “tls” into the search bar.
  2. From the list, navigate to “security.tls.version.min”.
  1. Select the pencil icon on the far right to edit the item, then input “0” as the value. Next, repeat the same process for ”security.tls.version.fallback-limit”.

Another way to bypass encryption protocols in your browser is by changing your browser’s privacy settings. 

To change your Firefox Privacy & Security Settings::

  1. Open your Firefox menu, then navigate to Options and then  Privacy & Security.
privacy setting firefox
  1. Under the Security section, deselect ”Block dangerous and deceptive content”. 

If the error still hasn’t been resolved, chances are it’s a server-related issue. Most often, this happens when a site is using the RC4-only cipher suite.

Some ciphers, such as the RC4, are no longer supported by major browsers due to vulnerabilities. You can run an SSL check to verify that your SSL certificate isn’t using outdated ciphers.

To perform an SSL Check, you can use the free SSL check tool Qualys SSL Labs. Here’s a link to the SSL Check tool to get you started.

ssl server test

Enter your domain into the Hostname field then click on “Submit”. You also have the option to hide public results if that’s what you prefer. It could take a minute or two to scan the site’s SSL/TLS configuration on your web server.

qualys ssl report

Once scanned, SSL Labs will assign you an SSL server rating, any grade from an A to an F. You should always be aiming for an A. This means both the SSL and intermediate certificates are set up correctly. It also shows that the webserver host, like WordPress, that you might be using is up to current specifications. 

If you click on the IP address, you’ll be shown a brief summary of that server’s rating. 

ssl error code report

For more information on SSL Labs SSL checks, their official guide can be found here.

That’s about it in bypassing encryption protocols through your privacy settings. Generally, if you aren’t the site owner, the only other course of action is to contact them to let them know about the problem you’ve experienced on their site – and, helping them get to the bottom of it by sharing this guide with them. 😊

You might also be interested in SSL/TLS certificate errors.

Check If It’s A Server Side Problem

In the case that the error is only appearing on one website, this is likely a server-side issue. Only the server admin can resolve this issue. 

Usually, this only happens when a website is still using RC4-Only Cipher Suite, and the settings with the server “security.tls.unrestricted_rc4_fallback” preference is toggled to false.

Frequently Asked Questions (You Might Also Ask)

What does error code SSL_error_no_cypher_overlap mean?

The “SSL_ERROR_NO_CYPHER_OVERLAP” is an error code unique to Firefox. Other browsers have these errors as well but typically use different codes. This error happens when Firefox fails to get the proper security information from the website you tried to connect to. This can happen for reasons of an outdated browser version, misconfigured SSL3 and TLS web browser settings, or it could be completely server-sided.

What does Pr_end_of_file_error mean?

The PR_END_OF_FILE_ERROR (Secure Connection Failed) appears when some Mozilla Firefox users attempt to visit a certain website. This error essentially means that the browser wasn’t able to establish a secure connection because all cypher suites failed.

What is a cypher mismatch?

This issue means that your browser cannot establish a secure connection with a web server that uses HTTPS and SSL.

How do I bypass “secure connection failed”?

To fix this, you need to visit the settings option of whichever security software that you are using and locate the SSL scanning feature of the software. 

Once you find it, uncheck the box that indicates if it is enabled. Once the feature is disabled on your security software, you should try revisiting the website.

What causes “secure connection failed”?

Sometimes the ‘Secure Connection Failed’ error may occur on Firefox if Firefox finds the website to be dangerous or untrustworthy. That is why Firefox browser testing is so critical. If Firefox approves the website, it means that there’s a problem with the SSL connection.

Sometimes the ‘Secure Connection Failed’ error may occur on Firefox if Firefox finds the website to be dangerous or untrustworthy. A website that uses HTTPS:// at the start of its URL indicates that it is a secure website. When Firefox doesn’t find a website secure, it will trigger an error displaying “Secure Connection Failed”.

What is “secure connection failed”?

Secure Connection Failed error is typically related to the security certificate (otherwise known as SSL) not being valid, expired, or simply missing. This notification quite often has merit, as the browser tries to warn that the connection is not secure, and you might suffer from serious issues if you proceed.

How do you solve not connecting a potential security problem?

To fix the “Secure Connection Failed” error in Mozilla Firefox:

1. Select “Continue With an Insecure Connection”.
2. Add the site to your List of Trusted Sites.
3. Temporarily disable your Antivirus and Firewall.
4. Clear the SSL State.
5. Clear Your Browsing History.
6. Permit Firefox to Trust Root Authorities.
7. Change Your Security Settings.

Summary – Easily Managing SSL Certificates & Resolving Errors

Running into issues especially with SSL certificate validation is not something anyone enjoys waking up to especially because getting to the bottom of what’s causing it can take some time. Fortunately, since you made it to the end of this guide – you should have been able to confidently ensure that you & your website visitors no longer encounter this error.

Here at RunCloud, we’re on a mission to make server management and deployments easier. Part of this, of course, naturally has to include SSL certificates. That’s why we offer AutoSSL to automatically handle deploying new SSL certificates for new domains that are added to your web applications (perfect for WaaS or SaaS businesses).

Have any additional questions about fixing this SSL error or just want to join the conversation? Leave a comment below or Tweet at us (we’re @runcloud) 💬