Amazon Linux AMI Security Advisory: ALAS-2012-130
Advisory Release Date: 2012-10-08 10:39 Pacific
Advisory Updated Date: 2014-09-14 17:07 Pacific
Munin before 2.0.6 stores plugin state files that run as root in the same group-writable directory as non-root plugins, which allows local users to execute arbitrary code by replacing a state file, as demonstrated using the smart_ plugin.
Run yum update munin to update your system.