Amazon Linux AMI Security Advisory: ALAS-2015-467
Advisory Release Date: 2015-01-08 11:44 Pacific
A flaw was found in the way mailx handled the parsing of email addresses. A syntactically valid email address could allow a local attacker to cause mailx to execute arbitrary shell commands through shell meta-characters and the direct command execution functionality. (CVE-2004-2771 , CVE-2014-7844 )
Note: Applications using mailx to send email to addresses obtained from untrusted sources will still remain vulnerable to other attacks if they accept email addresses which start with "-" (so that they can be confused with mailx options). To counteract this issue, this update also introduces the "--" option, which will treat the remaining command line arguments as email addresses.
Run yum update mailx to update your system.