How the Firefox SSL_ERROR_NO_CYPHER_OVERLAP Appears
This SSL_ERROR_NO_CYPHER_OVERLAP error can appear when you connect to an older website that lacks updated security credentials, thus the acronym SSL, which stands for Secure Sockets Layer. You’ll know that you’ve run into SSL_ERROR_NO_CYPHER_OVERLAP when you see an error message that says: You will also see a tip that explains the “authenticity of the received data cannot be verified,” and to contact the owner(s) of the website to inform them of this. Granted, it may not be a website issue at all––the error code will also appear if your version of Firefox is misconfigured or out of date.
Cause of the SSL_ERROR_NO_CYPHER_OVERLAP Firefox Error
Aside from a website potentially experiencing server-side SSL issues, it’s possible your Firefox settings are causing a miscommunication between the website server and your computer. This is a far likelier case if many different websites are throwing the error code SSL_ERROR_NO_CYPHER_OVERLAP. You should always keep Firefox up to date anyhow, but an outdated version of Firefox is a potential cause of Firefox error SSL_ERROR_NO_CYPHER_OVERLAP appearing. If either TLS or SSL3 are disabled or otherwise misconfigured in your Firefox TLS settings, the error code will also commonly spring up. Finally, any website that uses RC4 (Rivest Cipher 4) in its encryption will run into issues with Firefox TLS no matter what. This is because RC4 was prohibited from TLS in 2015.
How to Fix SSL_ERROR_NO_CYPHER_OVERLAP
If this error has appeared, here are somethings you can do to fix it and get back to browsing: If it’s set to something else, select the pencil icon to the far right of security.tls.version.max and change the number to 4.
