XMLValidator is not thread-safe due to the fact that a single validating parser is used for all calls to validate(). The parser should be created inside of validate() instead:

https://github.com/jboss-switchyard/core/blob/master/validate/src/main/java/org/switchyard/validate/xml/XmlValidator.java#L204
https://github.com/jboss-switchyard/core/blob/master/validate/src/main/java/org/switchyard/validate/xml/XmlValidator.java#L204