In Apache Xerces-C XML Parser library before 3.2.1, processing of external DTD paths can result in a null pointer dereference under certain conditions.
https://lists.debian.org/debian-lts-announce/2018/03/msg00032.html
https://kc.mcafee.com/corporate/index?page=content&id=SB10365
http://xerces.apache.org/xerces-c/secadv/CVE-2017-12627.txt