Another cgiemail bug

[sec <vulns () sm detack de>]

Yet another cgiemail and others bug.
Not much to report, so we'll keep it concise.
cgiemail: http://web.mit.edu/wwwdev/cgiemail/

Discussion:
It's on open relaying bug. This vulnerability affects cgiemail and a lot
of other web/mail applications, we are concentrating on cgiemail because
it is considered safe. The same kind of exploit can be performed on many
similar apps using the blessed "sendmail -t" to send the mail and avoid
the bad attacker getting a shell.

Details:
The problem is very few developers filter the new line code "%0a". When
posting data to the web/mail application, the remote user can take one of
the predefined variables and add "%0a" followed by additional fields
decoded by sendmail. For example CC: or Bcc: and so on. The result is that
the mail is going to a lot of other addresses.

Example:
POST

/cgi-bin/cgiemail?required-webmaster=xxx () xxx com&required-from=zzz () zzz com&
required-subject=spam%0aCC:address1 () smap com%20address2 () smap com%20address3 () smap com&
comments=spam%20message

Simple, clear enough.


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