XML External Entity Reference (XXE) vulnerability can lead to a Server Side Request Forgery attack in gematik app-referencevalidator

The reference validator is a tool to perform advanced validation of FHIR resources for TI applications and interoperability standards. The profile location routine in the referencevalidator commons package is vulnerable to `XML External Entities` attack due to insecure defaults of the used Woodstox WstxInputFactory. A malicious XML resource can lead to network requests issued by referencevalidator and thus to a `Server Side Request Forgery` attack. The vulnerability impacts applications which use referencevalidator to process XML resources from untrusted sources. The problem has been patched with the 2.5.1 version of the referencevalidator. Users are strongly recommended to update to this version or a more recent one. A pre-processing or manual analysis of input XML resources on existence of DTD definitions or external entities can mitigate the problem.