The PDORow implementation in PHP before 5.3.9 does not properly interact with the session feature, which allows remote attackers to cause a denial of service (application crash) via a crafted application that uses a PDO driver for a fetch and then calls the session_start function, as demonstrated by a crash of the Apache HTTP Server.
https://bugzilla.redhat.com/show_bug.cgi?id=783605
https://bugs.php.net/bug.php?id=55776
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