bugtraq - RE: Re: Cisco VPN Concentrator IKE resource exhaustion DoS Advisory

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Message-ID: <ADE211476268A0489F38792F620D6863577038@bekexch.corporate.bekinc.net>
Date: Fri, 11 Aug 2006 12:57:58 -0400
From: "Lance Seelbach" <lance@...inc.net>
To: <henry.sieff@...il.com>, <bugtraq@...urityfocus.com>
Subject: RE: Re: Cisco VPN Concentrator IKE resource exhaustion DoS Advisory

In reviewing the "fine print" of the Cisco response, their
recommendations fall in the category of a workaround, since the
underlying "vulnerability" is really a flaw in the IKE protocol.  Fix
the protocol and you can fix the "vulnerability".  But that would
require that every vendor who uses IKE to make changes too, which seems
to make this a much broader issue than Cisco.

L

-----Original Message-----
From: henry.sieff@...il.com 

Cisco recommends a workaround which essentially sets a limit on the
number of outstanding SA's and drops new SA requests if they exceed that
limit (outlined in
http://www.cisco.com/en/US/products/sw/iosswrel/ps5207/products_feature_
guide09186a0080229125.html)

It seems to me that this will not accomplish much - presumably the
determined attacker will simply continue to send packets - as soon as
the number of SA'ss drops below that limit the attacker will simply fill
up the queue again. Am I missing something about the vulnerability or
the supposed fix from Cisco?