I found an old device. After resetting it to factory default it was still imposible to access the webinterface, because of an unsupported protocol error (ERR-SSL-VERSION-OR-CIPHER-MISMATCH).

The ERR SSL VERSION OR CIPHER MISMATCH error in a Dutch Vivaldi browser

This error indicates that the server (the device in this case) only support old SSL/TLS protocols, so old that your browser won't open it any longer. Simply because hackers can easily perform an man-in-the-middle-attack.

The manufactor of the device released new firmware which support newer versions. But it was only possible to install via the web interface. In this short guide I will tell how temporary work a round this security system of the browser.

First step, install Mozilla Firefox when not present yet on your computer. Open Firefox and go to the special configuration by typing about:config in the location bar.

Typ about:config in the location bar

Search for security.tls.version.min and note down the current value (in my case it was 3). Change it to 1.

Caution: This will break down a security layer in Firefox! It is very important to revert this change after the job is finised. Make sure you are on a trusted network, when possible only connected with the target device so your network traffic can not be intercepted by others.

security-tls-version-min on the about:config page

Restart Firefox and open the device page. Expect an SSL warning because the certificate is usaly expired and/or self signed. Do your job (in this case update the firmware). Revert the change.

SSL/TLS error in Dutch Firefox

Important: Do not forget to revert the change on the about:config. Do never connect to the public internet with a low tls version min config!

19-06-2023 EN ERR_SSL_VERSION_OR_CIPHER_MISMATCH ERR-SSL-VERSION-OR-CIPHER-MISMATCH Chrome Vivaldi tls ssl unsupported old protocol
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