USN-2455-1: bsd-mailx vulnerability

7 January 2015

bsd-mailx vulnerability

A security issue affects these releases of Ubuntu and its derivatives:

  • Ubuntu 14.10
  • Ubuntu 14.04 LTS
  • Ubuntu 12.04 LTS
  • Ubuntu 10.04 LTS

Summary

bsd-mailx could be made to run programs if it parsed a specially crafted email address.

Software Description

  • bsd-mailx - simple mail user agent

Details

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 “-”. In addition, specifying sendmail options after the “–” separator is no longer supported, existing scripts may need to be modified to use the “-a” option instead.

Update instructions

The problem can be corrected by updating your system to the following package versions:

Ubuntu 14.10
bsd-mailx - 8.1.2-0.20131005cvs-1ubuntu0.14.10.1
Ubuntu 14.04 LTS
bsd-mailx - 8.1.2-0.20131005cvs-1ubuntu0.14.04.1
Ubuntu 12.04 LTS
bsd-mailx - 8.1.2-0.20111106cvs-1ubuntu0.1
Ubuntu 10.04 LTS
bsd-mailx - 8.1.2-0.20090911cvs-2ubuntu1.1

To update your system, please follow these instructions: https://wiki.ubuntu.com/Security/Upgrades.

In general, a standard system update will make all the necessary changes.

References