The vulnerability stems from XML parser configurations in various XStream drivers that did not disable external entity processing. Each listed function is responsible for creating XML parser factories/builders for their respective XML processing implementations (DOM, DOM4J, JDOM, StAX). The functions are vulnerable because they didn't implement security settings like disabling DTD processing or external entity expansion, which are standard XXE mitigations. The high confidence comes from: 1) The CVE explicitly listing these drivers 2) XStream's changelog showing 1.4.9 addressed XXE in these components 3) Security best practices for XML parsing requiring these protections.