Rule:  


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Sid:
5723

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Summary:
A buffer overflow exists in the SMB (Server Message Block) Protocol implementation in Microsfot Windows NT, Windows 2000, and Windows XP that allows attackers to cause a denial of service via a NetShareEnum request.

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Impact:
An attacker can cause the target system to lock up and require manual reboot.  With more research, an attacker may be able to exploit this buffer overflow and execute arbitrary code, but this research has not been made public at this time.

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Detailed Information:
SMB on a vulnerable system may crash if it recieves a specially crafted packet containing a NetServerEnum, NetServerEnum2, or NetServerEnum3 transaction request.  If either the paramaters "Max Parameter Count" or "Max Data Count" are set to 0, then a vulnerable system will crash.  NetServerEnum requests require an authorized user account, however NetServerEnum2 and NetServerEnum3 require anonymous access.  Anonymous access is enabled by default.  This signature looks for both the "Max Parameter Count" and "Max Data Count" set to 0.

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Affected Systems:
Windows 2000 SP3
Windows 2000 SP4
Windows XP SP1
Windows XP SP2
Windows 2003 SP1

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Attack Scenarios:
Simple. An attacker would use one of the various publicly available tools to launch this attack.

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Ease of Attack:
Numerous tools, including a windows binary (SMBDie.exe), have been made publicly available to exploit the denial of service portion of this vulnerability.

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False Positives:
This rule may generate an event on functions other than NetServerEnum, NetServerEnum2, or NetServerEnum3.  An SMB decoder is not available in Snort, thus verification that the function being called is not feasable.

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False Negatives:
None Known

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Corrective Action:
Install the patches available from Microsoft.  The patches are listed in Microsoft's advisory for this vulnerability.

www.microsoft.com/technet/security/bulletin/MS02-045.asp

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Contributors:
Sourcefire Research Team
Brian Caswell <bmc@snort.org>
Nigel Houghton <nigel.houghton@sourcefire.com>

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Additional References:

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