ext/xml/xml.c in PHP before 5.3.27 does not properly consider parsing depth, which allows remote attackers to cause a denial of service (heap memory corruption) or possibly have unspecified other impact via a crafted document that is processed by the xml_parse_into_struct function.
https://bugzilla.redhat.com/show_bug.cgi?id=983689
https://bugs.php.net/bug.php?id=65236
http://www.ubuntu.com/usn/USN-1905-1
http://www.debian.org/security/2013/dsa-2723
http://support.apple.com/kb/HT6150
http://secunia.com/advisories/54165
http://secunia.com/advisories/54163
http://secunia.com/advisories/54104
http://secunia.com/advisories/54071
http://rhn.redhat.com/errata/RHSA-2013-1063.html
http://rhn.redhat.com/errata/RHSA-2013-1062.html
http://rhn.redhat.com/errata/RHSA-2013-1061.html
http://rhn.redhat.com/errata/RHSA-2013-1050.html
http://rhn.redhat.com/errata/RHSA-2013-1049.html
http://php.net/archive/2013.php#id2013-07-11-1
http://php.net/ChangeLog-5.php
http://lists.opensuse.org/opensuse-security-announce/2013-08/msg00007.html
http://lists.opensuse.org/opensuse-security-announce/2013-08/msg00006.html
http://lists.opensuse.org/opensuse-security-announce/2013-07/msg00034.html
http://git.php.net/?p=php-src.git%3Ba=commit%3Bh=7d163e8a0880ae8af2dd869071393e5dc07ef271