Memory leak in the timezone functionality in PHP before 5.3.9 allows remote attackers to cause a denial of service (memory consumption) by triggering many strtotime function calls, which are not properly handled by the php_date_parse_tzfile cache.
http://www.php.net/ChangeLog-5.php#5.3.9
http://secunia.com/advisories/48668
http://lists.opensuse.org/opensuse-security-announce/2012-03/msg00016.html
http://lists.opensuse.org/opensuse-security-announce/2012-03/msg00013.html