UserAgent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Safari/537.36

Example URL:

Steps to reproduce the problem:
1. Setup a server (works for nginx/1.11.6) with who hosts (a.example.com and b.example.com) supporting HTTP/2 and the same certificate (*.example.com).
2. Visit https://a.example.com/
3. Visit https://b.example.com/ fails with 421 Misdirected Request

What is the expected behavior?
All sites (a.example.com and b.example.com) works.

What went wrong?
Chrome uses for https://b.example.com/ the same HTTP/2 connection that it creates for https://a.example.com/. As I know, this RFC says that this behavior is correct, but in fact web servers (nginx/1.11.6 is an example) do additional checks and return an error if given host doesn't match the host client used in TLS negotiation.

Did this work before? N/A 

Chrome version: 56.0.2924.87  Channel: stable
OS Version: gentoo
Flash Version: 

One workaround may be to create new connection after receiving 421, but some older versions of nginx don't have explicit code for misdirected request and return generic 400 Bad Request.

Of course if I am right about RFC this is not a bug of chrome browser, but trouble in web servers. Unfortunately, bad web servers exist so I decided to send this issue to you too.