Rule: 

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Sid: 
3017

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Summary: 
An oversized request was sent to a WINS server.

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Impact: 
Client-supplied data is written to client-specified locations in memory,
allowing for arbitrary code execution. Since WINS servers run with
administrative privileges, this allows an attacker to gain
administrative access remotely without any prior authentication.

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Detailed Information:
Vulnerable WINS servers write client-supplied data to a client-supplied
memory address. This allows clients to supply arbitrary code for
execution with administrative privileges. This attack does not require authentication.

In order to reduce false positives, the rule looks for requests that are
greater than 204 bytes. As the maximum length of a hostname is 192
bytes, and a standard request has 12 bytes of headers, no standard
request should exceed this length. Additionally, this rule checks to see
if particular flags that are required to exploit this vulnerability are
set in the client request.

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Affected Systems:
Microsoft Windows servers running the WINS service.

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Attack Scenarios: 
Since WINS clients are programmed to not exceed the maximum length for a
request, an attacker would need to use a script which generated
malformed WINS requests.

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Ease of Attack: 
Simple; exploits exist.

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False Positives:
This rule will generate false positives when replication occurs.
Additionally, there may be unknown scenarios which generate false positives.

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False Negatives:
None known.

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Corrective Action: 
See the Microsoft Knowledge Base article referenced below.

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Contributors: 
Sourcefire Research Team
Brian Caswell <bmc@sourcefire.com>
Alex Kirk <alex.kirk@sourcefire.com>

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Additional References:
http://support.microsoft.com/kb/890710

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