Assume the following scenario:
- A web page is accessed using Google Chrome.
- The connection setup fails with the following error message:
This website cannot provide a secure connection test.intra.adcslabor.com has sent an invalid response. Try to run the Windows network diagnostics. ERR_SSL_PROTOCOL_ERROR
The error only occurs with Chrome. However, Internet Explorer, Firefox and Microsoft Edge (both the "Spartan" variant and the newer Chromium-based "Anaheim" variant) connect to the page without generating an error message.
Cause
Chrome has been using HTTP over SSL (HTTPS) as its default protocol since the first release in 2021 (version 88.0.4324.190 for Windows, and 88.0.4324.192 for Mac).
The page accessed in this case was running on a non-standard port and did not have SSL enabled at all.
Therefore, the web server responded to the SSL Client Hello with HTTP error code 400 (Bad Request).
All other browsers fall back to HTTP and have therefore called the page correctly, but of course without the actually desired SSL encryption.
It is to be expected that Microsoft Edge will exhibit similar behavior in the near future.
Solution
The website should be switched to SSL. See also article "Manually requesting a web server certificate„.
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