bugtraq - New Bug KESM in GoogleTalk

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Date: 9 Nov 2005 00:01:40 -0000
From: natalylopez380@...mail.com
To: bugtraq@...urityfocus.com
Subject: New Bug KESM in GoogleTalk

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@...il.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 :-)