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Re: Sendmail MIME DoS vulnerability
From: Gadi Evron (gelinuxbox.org)
Date: Wed Jun 21 2006 - 13:32:00 CDT
On Tue, 20 Jun 2006, Jain, Siddhartha wrote:
> I am trying to understand how the below mentioned sendmail
> The description says that the DoS occurs when sendmail goes in a deeply
> nested malformed MIME message and uses the MIME 8-bit to 7-bit
> conversion function. Under what conditions would sendmail use the MIME
> 8-bit to 7-bit function? Only when the remote MTA doesn't understand
> 8-bit MIME, right?
> That would mean that a malicious user would have to force the victim MTA
> to relay the malformed mail to a MIME 7-bit-only MTA for the attack to
> succeed. This probably means that open relays and ISP SMTP servers are
> more vulnerable than purely incoming SMTP servers.
> I am just trying to make sense of the advisory and the possible threat
> of exploit.
I didn't understand at first, either. As I attributed it to the DATA part
of the message. Apparently sendmail is smart enough to prevent the message
from not reaching the other side due to breakage using this. But I don't
get it completely yet.
> - Siddhartha