Here is the regression test:
%test Invalid HTTP Request Line (960911) - Test 2
This test uses backslashes instead of forward slashes.
GET \index.html HTTP\1.0
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:188.8.131.52) Gecko/20060909 Firefox/184.108.40.206
When sniffing the traffic over the wire, you will notice that the \index.html is being sent as simply "index.html" (backslash disappears), and the HTTP protocol version is sent as HTTP[\x01].0 - (\1 is sent as \x01 ASCII).
My guess is that the test needs some escaping for the backslash characters.
I ran a quick search on other tests, and none of them has a similar problem.
Fixed in v2.2.8