What is your listener(s) configuration in undertow subsystem?
are you using SSL?
What is exact version of WildFly you are using?
The version we ware testing with is 8.1.0.CR2.
We do get some https requests, a small percentage, but we haven't configured ssl on the server yet.
The configuration for undertow right now is the default.
Can you try with 8.1.0.Final that was released today? There ware few fixes in connection handling for undertow.
What strikes me as strange is that problems you are seeing we saw only with https requests and you say you have few of them but don't have ssl configured in subsystem...
What is exact version of JDK you are using and on what platform?