The REXML parser in Ruby 1.9.x before 1.9.3-p550, 2.0.x before 2.0.0-p594, and 2.1.x before 2.1.4 allows remote attackers to cause a denial of service (memory consumption) via a crafted XML document, aka an XML Entity Expansion (XEE) attack.
https://support.apple.com/HT205267
http://www.ubuntu.com/usn/USN-2397-1
http://www.securityfocus.com/bid/70935
http://www.oracle.com/technetwork/topics/security/linuxbulletinjan2016-2867209.html
http://www.mandriva.com/security/advisories?name=MDVSA-2015:129
http://www.debian.org/security/2015/dsa-3159
http://www.debian.org/security/2015/dsa-3157
http://secunia.com/advisories/62748
http://secunia.com/advisories/62050
http://secunia.com/advisories/61607
http://rhn.redhat.com/errata/RHSA-2014-1914.html
http://rhn.redhat.com/errata/RHSA-2014-1913.html
http://rhn.redhat.com/errata/RHSA-2014-1912.html
http://rhn.redhat.com/errata/RHSA-2014-1911.html
http://lists.opensuse.org/opensuse-updates/2015-01/msg00004.html
http://lists.opensuse.org/opensuse-updates/2015-01/msg00000.html
http://lists.opensuse.org/opensuse-updates/2014-12/msg00035.html
http://lists.apple.com/archives/security-announce/2015/Sep/msg00008.html