The openssl_encrypt function in ext/openssl/openssl.c in PHP 5.3.9 through 5.3.13 does not initialize a certain variable, which allows remote attackers to obtain sensitive information from process memory by providing zero bytes of input data.
https://bugs.php.net/bug.php?id=61413
https://bugs.launchpad.net/ubuntu/+source/php5/+bug/1099793
http://www.ubuntu.com/usn/USN-1702-1
http://openwall.com/lists/oss-security/2013/01/18/6
http://git.php.net/?p=php-src.git%3Ba=commit%3Bh=270a406ac94b5fc5cc9ef59fc61e3b4b95648a3e