bugtraq - Evolution Emailer DoS

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Message-ID: <20060301165840.GA26720@ftp.linux.org.uk>
Date: Wed, 1 Mar 2006 16:58:40 +0000
From: Alan Cox <alan@....linux.org.uk>
To: bugtraq@...urityfocus.com
Subject: Evolution Emailer DoS

About 7 weeks ago an automated mailing list spewed a large but valid email
containing a lot of URLS and other formatting. When this email is fed into
evolution the behaviour it causes leads evolution to expand dramatically in 
size and eat vast amounts of CPU time. If you've got a lot of patience and
memory it is eventually rendered correctly (many minutes and many gigs)

The attack in question can be triggered with a large but valid plain text
email containing no unusual features. It is possible to perform the attack with
a somewhat smaller message than the one given but the one provided should
suffice for analysis and testing.

Worse, and the reason this becomes more than irritating is that evolution
tries to be smart when it is killed or dies. On restarting it will go to
great trouble to attempt to restart in the same position it died or was shut
down - which triggers the DoS again each time evolution is opened.

This bug was reported to vendor-sec January 18th, and acknowledged January
19th as CVE-2006-0040. A request for any follow up details was posted end 
of February. No vendor has chosen to provide any more information which I 
find disappointing.

The email that triggered the original accidental discovery is available at

	http://zeniv.linux.org.uk/~alan/destroy-evolution.mbox

As the problem appears to come from gtkhtml it is likely that other gtkhtml
users may be similarly afflicted.

Recommendations:
	Block large text emails with many URLS using a filter rule
	Ask your vendor awkward questions
	or switch mailer

Happy St Davids Day
Alan