expat 2.1.0 and earlier does not properly handle entities expansion unless an application developer uses the XML_SetEntityDeclHandler function, which allows remote attackers to cause a denial of service (resource consumption), send HTTP requests to intranet servers, or read arbitrary files via a crafted XML document, aka an XML External Entity (XXE) issue. NOTE: it could be argued that because expat already provides the ability to disable external entity expansion, the responsibility for resolving this issue lies with application developers; according to this argument, this entry should be REJECTed, and each affected application would need its own CVE.
http://openwall.com/lists/oss-security/2013/02/22/3
http://www.openwall.com/lists/oss-security/2013/04/12/6
http://securitytracker.com/id?1028213
http://www.securityfocus.com/bid/58233
https://security.gentoo.org/glsa/201701-21
https://support.apple.com/kb/HT212814
https://support.apple.com/kb/HT212815
https://support.apple.com/kb/HT212819
https://support.apple.com/kb/HT212807
https://support.apple.com/kb/HT212804
https://support.apple.com/kb/HT212805
http://seclists.org/fulldisclosure/2021/Sep/39
http://seclists.org/fulldisclosure/2021/Sep/38
http://seclists.org/fulldisclosure/2021/Sep/35
http://seclists.org/fulldisclosure/2021/Sep/34
http://seclists.org/fulldisclosure/2021/Sep/33
http://seclists.org/fulldisclosure/2021/Sep/40
https://lists.apache.org/thread.html/[email protected]%3Cannounce.apache.org%3E
https://lists.apache.org/thread.html/[email protected]%3Cusers.openoffice.apache.org%3E
http://www.openwall.com/lists/oss-security/2021/10/07/4
http://seclists.org/fulldisclosure/2021/Oct/61