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You’ll see the SSL_ERROR_NO_CYPHER_OVERLAP in Firefox if it can’t get the required security data from a website. While this is often because a site won’t have a current Secure Sockets Layer (SSL) certificate, you may also find this is due to a miscommunication between browser and server.

If your browser’s TLS and SSL settings don’t align with what the server expects, you’ll see the SSL_ERROR_NO_CYPHER_OVERLAP. This can be fixed in two ways:

  • Setup SSL and TLS settings
  • Carry out a temporary bypass of your browser’s configuration settings.
  • Note that we’re not going to cover some super basic fixes here. For example, you won’t find information on making sure you update your browser, or deactivating your firewall and anti-virus software. These should be second nature, and we’d recommend you tackle the below steps with a current version of your browser, with no other software able to impact your session.

    1. Setup SSL/TLS Settings

    For secure sites to function, they need active, accurate and current TLS3 and SSL3 connections. If the browser falters here, you’ll see the SSL_ERROR_NO_CYPHER_OVERLAP in Firefox.

    To resolve this, you’ll need to access Firefox’s browser configuration settings. You’ll do this through using about:config within the address bar:

    In most situations, this will show you a warning: “Proceed With Caution” will be the most common, but it could display other variations. Regardless, this is Firefox’s way to tell you that whatever you do here could introduce problems. You can choose to accept the risk and continue, which will take you to your preferences screen.

    On this screen, use the search bar to filter entries for “tls”:

    Also, do the same for “ssl3”:

    For both of these searches, you’ll want to reset any bold values. This ‘bolding’ denotes a recent change that you need to be aware of.

    While you’re here, you’ll also want to make sure two entries only show as “false”:

  • security.ssl3.dhe_rsa_aes_128_sha
  • security.ssl3.dhe_rsa_aes_256_sha
  • These shouldn’t need your input, but know that they are essential security settings. If they don’t have a false value, you’ll need to make sure they do in order to fix the SSL_ERROR_NO_CYPHER_OVERLAP in Firefox.

    2. You can bypass your browser configuration and security

    For the majority of cases, you’ll either deal with an unsecure website, or a change in your browser settings. However, you may want to bypass some of your security settings to make sure that you don’t have an issue.

    Note that we don’t recommend this step as a permanent fix. Your browser’s security configurations help protect you and your data from malicious intent. As such, you’ll want to revert things back once you carry out a test, and seek out a permanent resolution to the SSL_ERROR_NO_CYPHER_OVERLAP in Firefox.

    Regardless, you’ll need to head back to the about:config screen in Firefox. This time, search for the security.tls.version.min entry:

    You can enter zero (0) values using the pencil icon. The tick icon will save your changes. This should resolve the SSL_ERROR_NO_CYPHER_OVERLAP in Firefox, but you can also enter into your browser’s general settings pane:

    Under the Privacy & Security pane, scroll to the Security section, and look for the Block dangerous and deceptive content option:

    If you untick this, you’ll bypass your browser’s encryption protocols, which will let you see if you can fix the SSL_ERROR_NO_CYPHER_OVERLAP in Firefox.


    The SSL_ERROR_NO_CYPHER_OVERLAP in Firefox – sometimes the ERR_SSL_VERSION_OR_CIPHER_MISMATCH error in Google Chrome – can stump you. However, it is usually easy to fix. The problem is often due to an outdated SSL certificate. Even so, it’s a good idea to check over your browser’s TLS and SSL settings to see if this will resolve the issue.

    While we talk about bypassing your browser’s security configurations, it’s not a recommended step. It’s good for a temporary resolution, but you’ll want to find a more permanent fix over the longer term.

    Do you have any questions about the SSL_ERROR_NO_CYPHER_OVERLAP in Firefox? You can ask questions in the comment section!

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