Apache CXF JAX-RS implementation provides a number of Atom MessageBodyReaders. These readers use Apache Abdera Parser to parse Atom feeds or Entries, with this Parser expanding XML entities by default. This represents a major XXE risk.
External References:
http://cxf.apache.org/security-advisories.data/CVE-2016-8739.txt.asc?version=1&modificationDate=1482164360575&api=v2