Amazon Linux AMI Security Advisory: ALAS-2018-964
Advisory Release Date: 2018-03-07 21:14 Pacific
It was discovered that the memcached daemon listened on UDP port 11211 by default. An attacker could use memcached for UDP amplification denial-of-service attacks. The UDP port has been disabled by default, but can still be enabled.
It was discovered that the memcached connections using UDP transport protocol can be abused for efficient traffic amplification distributed denial of service (DDoS) attacks. A remote attacker could send a malicious UDP request using a spoofed source IP address of a target system to memcached, causing it to send a significantly larger response to the target. (CVE-2018-1000115 )
Run yum update memcached to update your system.