dependency:tree goal output shows that jbossws-cxf-client (and transitively other modules too) depends on two versions of JBoss JAX-WS API:

org.jboss.spec.javax.xml.ws:jboss-jaxws-api_2.2_spec:jar:2.0.2.Final:compile
org.jboss.spec.javax.xml.ws:jboss-jaxws-api_2.3_spec:jar:1.0.0.Final:compile

The former is brought in by:

   +- org.jboss.ws.cxf:jbossws-cxf-transports-undertow:jar:5.2.5-SNAPSHOT:compile
   |  \- org.jboss.ws.projects:jaxws-undertow-httpspi:jar:1.0.1.Final:compile
   |   +- org.jboss.spec.javax.xml.ws:jboss-jaxws-api_2.2_spec:jar:2.0.2.Final:compile

I guess we should stick to the newer one which would mean add some dependency exclude or update jaxws-undertow-httpspi to new API version stream (I vote for this)

Whole dependency tree at https://github.com/jbliznak/jbws-dependency-trees/blob/jdk11-after/jbossws-cxf-client_module.txt