Amazon Linux AMI Security Advisory: ALAS-2015-521
Advisory Release Date: 2015-05-06 15:14 Pacific
A denial of service flaw was found in the way Python's SSL module implementation performed matching of certain certificate names. A remote attacker able to obtain a valid certificate that contained multiple wildcard characters could use this flaw to issue a request to validate such a certificate, resulting in excessive consumption of CPU.
Run yum update python-tornado to update your system.