Amazon Linux AMI Security Advisory: ALAS-2012-52
Advisory Release Date: 2014-09-14 15:39 Pacific
It was found that the hashing routine used by libxml2 arrays was susceptible to predictable hash collisions. Sending a specially-crafted message to an XML service could result in longer processing time, which could lead to a denial of service. To mitigate this issue, randomization has been added to the hashing function to reduce the chance of an attacker successfully causing intentional collisions. (CVE-2012-0841 )
Run yum update libxml2 to update your system.