FULL PRODUCT VERSION :
java version "9.0.4"
Java(TM) SE Runtime Environment (build 9.0.4+11)
Java HotSpot(TM) 64-Bit Server VM (build 9.0.4+11, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 10.0.15063]

A DESCRIPTION OF THE PROBLEM :
We have an application that is started through Java Web Start. After upgrade of Jetty to 9.4.8, we have started noticing HTTP header parsing exceptions in our logs on the server. It turns out that those requests are being sent by Java Control Panel whenever it starts. It sends a HTTP request like this:

GET /jnlp/eclipseplugins.jsp HTTP/1.1
User-Agent
UA-Java-Version: 9.0.4
Cache-Control: no-cache
Pragma: no-cache
User-Agent: Java/9.0.4
Host: tas-cz-n24e.ca.com:8081
Accept: text/html, image/gif, image/jpeg, *; q=.2, */*; q=.2
Connection: keep-alive

And here is the answer from Jetty, which actually points at the User-Agent header above:

HTTP/1.1 400 Illegal character 0xA
Content-Type: text/html;charset=iso-8859-1
Content-Length: 64
Connection: close

<h1>Bad Message 400</h1><pre>reason: Illegal character 0xA</pre>

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Java not sending headers without value as per RFC 7230.

REPRODUCIBILITY :
This bug can be reproduced always.