PHP is an HTML-embedded scripting language commonly used with the Apache HTTP Server.
A buffer overflow flaw was found in the way PHP parsed deeply nested XML documents. If a PHP application used the xml_parse_into_struct() function to parse untrusted XML content, an attacker able to supply specially-crafted XML could use this flaw to crash the application or, possibly, execute arbitrary code with the privileges of the user running the PHP interpreter. (CVE-2013-4113)
All php53 users should upgrade to these updated packages, which contain a backported patch to resolve this issue. After installing the updated packages, the httpd daemon must be restarted for the update to take effect.