Rule:
alert udp $EXTERNAL_NET any -> $HOME_NET 500 (msg:"DOS ISAKMP invalid
identification payload attempt";  content:"|05|"; offset:16; depth:1;
byte_test:2,>,4,30; byte_test:2,<,8,30; reference:bugtraq,10004;
classtype:attempted-dos; sid:2486; rev:1;)

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Sid:
2486

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Summary:
This event is generated when an attempt is made to exploit a denial of service
(DoS) associated with tcpdump decoding of an isakmp payload.

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Impact:
A successful attack may cause a DoS of the host running tcpdump.

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Detailed Information:
The tcpdump decode of an isakmp packet with an identification payload may be
susceptible to a DoS attack.  This occurs because the code does not properly
convert the payload length field from network-to-host byte order. This may
cause tcpdump to crash when specific values are supplied to the payload length.

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Affected Systems:
Hosts running tcpdump versions 3.8.1 and earlier

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Attack Scenarios:
An attacker can create and send a malformed isakmp packet that may cause
a host running tcpdump and analyzing the packet to crash.

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Ease of Attack:
Simple. Exploit code exists.

--
False Positives:
None known.

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False Negatives:
None known.

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Corrective Action:
Upgrade to the latest non-affected version of the software.

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Contributors:
Sourcefire Research Team
Judy Novak <judy.novak@sourcefire.com>

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Additional References

Bugtraq:
http://www.securityfocus.com/bid/10004

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