Check the version of bsd-mailx
Please Install the Updated Packages.
It was discovered that bsd-mailx contained a feature that allowed syntactically valid email addresses to be treated as shell commands. A remote attacker could possibly use this issue with a valid email address to execute arbitrary commands. This functionality has now been disabled by default, and can be re-enabled with the 'expandaddr' configuration option. This update alone does not remove all possibilities of command execution. In environments where scripts use mailx to process arbitrary email addresses, it is recommended to modify them to use a '--' separator before the address to properly handle those that begin with '-'.
bsd-mailx on Ubuntu 14.10 , Ubuntu 14.04 LTS , Ubuntu 12.04 LTS , Ubuntu 10.04 LTS
Get the installed version with the help of detect NVT and check if the version is vulnerable or not.