Jessica Perry Hekman <[EMAIL PROTECTED]> writes:

> They said I should just use sendmail. I quoted them the comment in
> Defaults.py which explains that that's insecure, and they said it
> wasn't insecure on their server since their sendmail is just a
> wrapper around qmail.

When OUTGOINGMAIL = 'sendmail', TMDA sends mail with the sendmail
interface like such:

  /usr/sbin/sendmail -f 'envelope_sender' -- 'envelope_recipient' 

Thus, if someone sends you a message with some shell command as their
Return-Path, there is a chance it could be executed by the shell when
the above sendmail command is run.

I haven't examined this issue in depth, because the smtp method is
available which is not vulnerable to this type of attack.

My warning in the comments comes directly from Mailman which also
recommends against using sendmail.  In fact, in the latest Mailman
(2.1b3), using sendmail is no longer a configurable option.  You now
have to go edit some source code to enable it.  That's how strongly
they feel about it.

I know not whether this issue is MTA-independent or not.  It may very
well be that qmail can not be exploited in this way.
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