The XML parser (xmlparse.c) in expat before 2.1.0 computes hash values without restricting the ability to trigger hash collisions predictably, which allows context-dependent attackers to cause a denial of service (CPU consumption) via an XML file with many identifiers with the same value.
bugs.python.org/issue13703#msg151870
lists.apple.com/archives/security-announce/2013/Oct/msg00004.html
lists.apple.com/archives/security-announce/2015/Dec/msg00005.html
mail.libexpat.org/pipermail/expat-discuss/2012-March/002768.html
rhn.redhat.com/errata/RHSA-2012-0731.html
rhn.redhat.com/errata/RHSA-2016-0062.html
rhn.redhat.com/errata/RHSA-2016-2957.html
secunia.com/advisories/49504
secunia.com/advisories/51024
secunia.com/advisories/51040
sourceforge.net/projects/expat/files/expat/2.1.0/
sourceforge.net/tracker/?func=detail&atid=110127&aid=3496608&group_id=10127
www.debian.org/security/2012/dsa-2525
www.mandriva.com/security/advisories?name=MDVSA-2012:041
www.oracle.com/technetwork/topics/security/bulletinjul2016-3090568.html
www.securityfocus.com/bid/52379
www.ubuntu.com/usn/USN-1527-1
www.ubuntu.com/usn/USN-1613-1
www.ubuntu.com/usn/USN-1613-2
kc.mcafee.com/corporate/index?page=content&id=SB10365
support.apple.com/HT205637
www.tenable.com/security/tns-2016-20