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Google Talk EMail Notifition Denial Of Service

List: bugtraq
Subject: New Bug KESM in GoogleTalk
From: natalylopez380 () hotmail ! com
Date: 2005-11-09 0:01:40
Message-ID: 20051109000140.29652.qmail () securityfocus ! com
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Hi!! My name is Nataly Lopez, I'm a 17 years old girl living in Venezuela; I have \ always loved computer security because that's also my father's work. Well, the \ reason for me to post this is for telling you about a bug in Google Talk I discovered \ with my friend chris77 (#velug @ irc.freenode.net) this afternoon. Google Talk's \ excellent features allow the user to know when contacts send mails without \ configuring any passports, etc., well, you know that. What's really funny is: one can \ generate remote errors in the users' systems connected to Google Talk, and thus \ creating a kind of DoS. So Google Talk stops working if it has email notification \ enabled: it suffices to type this command in a Linux shell (nail must be installed of \ course):

echo kill | nail -s Kill -r "" victim@gmail.com

This instruction is quite simple, and will send an email to the user being connected \ to Google Talk from a certain "unknown sender", and as you can see, GoogleTalk \ Windows client cannot notify <> is sending an email. Therefore, an error windows \ appears on screen:

[ Google Talk encountered an internal error, and must now close. Ok to report this \ error to Google? ] [Yes] [No]

We called this bug KESM, which stands for "Killer Empty Sender Message" :) and one \ can easily implement it into a loop, keeping the victim busy clicking on the YES \ button and resetting his connection to Google Talk.

That's all for now folks :-)

Vulnerable software and versions

Configuration 1
− Google, Google Talk,
− Google, Google Talk,
− Google, Google Talk,
− Google, Google Talk,
− Google, Google Talk,
− Google, Google Talk,
− Google, Google Talk,, and previous

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