It was discovered that bsd-mailx, an implementation of the "mail" command, had an undocumented feature which treats syntactically valid email addresses as shell commands to execute.

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Debian Security Advisory DSA-3104-1                   This email address is being protected from spambots. You need JavaScript enabled to view it.
http://www.debian.org/security/                            Florian Weimer
December 16, 2014                      http://www.debian.org/security/faq
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Package        : bsd-mailx
CVE ID         : CVE-2014-7844

It was discovered that bsd-mailx, an implementation of the "mail"
command, had an undocumented feature which treats syntactically valid
email addresses as shell commands to execute.

Users who need this feature can re-enable it using the "expandaddr" in
an appropriate mailrc file.  This update also removes the obsolete -T
option.  An older security vulnerability, CVE-2004-2771, had already
been addressed in the Debian's bsd-mailx package.

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 stable distribution (wheezy), this problem has been fixed in
version 8.1.2-0.20111106cvs-1+deb7u1.

We recommend that you upgrade your bsd-mailx packages.

Further information about Debian Security Advisories, how to apply
these updates to your system and frequently asked questions can be
found at: https://www.debian.org/security/

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