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Re: Re: Cisco VPN Concentrator IKE resource exhaustion DoS Advisory



Thank you for the response.

My question is "is it even a workaround."

Cisco's solution is to have the VPN concentrator refuse new SA
requests once the number of pending SA requests exceeds the set
amount. But the symptom of the DOS is that no new SA's can be formed.
So the workaround produces the same results as the DOS .

On 8/11/06, Lance Seelbach <lance@xxxxxxxxxx> wrote:
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@xxxxxxxxx

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?