heirloom-mailx - security update

Two security vulnerabilities were discovered in Heirloom mailx, an
implementation of the mail command:

• CVE-2004-2771
  mailx interprets shell meta-characters in certain email
  addresses.
• CVE-2014-7844
  An unexpected feature of mailx treats syntactically valid email
  addresses as shell commands to execute.

Shell command execution can be re-enabled using the expandaddr
option.

Note that this security update does not remove all mailx facilities
for command execution, though. Scripts which send mail to addresses
obtained from an untrusted source (such as a web form) should use the
“–” separator before the email addresses (which was fixed to work
properly in this update), or they should be changed to invoke
“mail -t” or “sendmail -i -t” instead, passing the recipient addresses
as part of the mail header.

For the oldstable distribution (squeeze), these problems have been fixed in
version 12.4-2+deb6u1.

We recommend that you upgrade your heirloom-mailx packages.