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Lighttpd DoH server on the local network works with Brave browser but Firefox 123 complains that "TRR_FAILED"

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If I use the Apache server with an expired SSL certificate it works.

What am I missing?

If I use the Apache server with an expired SSL certificate it works. What am I missing?

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I updated Lighttpd and the problem is solved.

The origin of the error was its handling of empty request headers. It manifested in the logs with the message "invalid header value -> 400".