Undertow's default for the maximum number of HTTP parameter it parses in a GET or POST is 1000:

15:05:41,276 ERROR [io.undertow.request] (default task-17)
   Servlet request failed HttpServerExchange{ POST /***/*******/****}:
   java.lang.IllegalStateException: UT000047: The number of
   parameters exceeded the maximum of 1000

In the Undertow sources (https://github.com/undertow-io/undertow/blob/master/core/src/main/java/io/undertow/UndertowOptions.java), I found this to be a configurable option: "MAX_PARAMETERS".

Please allow changing some of these Undertow options through the WildFly standalone.xml. Tomaz Cerar asked me to create a ticket for this, based on the referenced forum thread.