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Title:      Malformed Request to RPC Endpoint Mapper can Cause RPC
            Service to Fail
Date:       10 September 2001
Software:   Microsoft(r) Windows NT(r) 4.0
Impact:     Denial of service
Bulletin:   MS01-048

Microsoft encourages customers to review the Security Bulletin at:
http://www.microsoft.com/technet/security/bulletin/MS01-048.asp.
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Issue:
======
The RPC endpoint mapper allows RPC clients to determine the port
number currently assigned to a particular RPC service. The Windows NT
4.0 endpoint mapper contains a flaw that causes it to fail upon
receipt of a request that contains a particular type of malformed
data. 

Because the endpoint mapper runs within the RPC service itself,
exploiting this vulnerability would cause the RPC service itself to
fail, with the attendant loss of any RPC-based services the server
offers, as well as potential loss of some COM functions. Normal
service could be restored by rebooting the server. 

Mitigating Factors:
====================
 - Standard security recommendations call for port 135 - the port
   on which the RPC endmapper operates - to be blocked at the
   firewall. If this were done, Internet-based attackers would not
   be able to exploit this vulnerability. 

Patch Availability:
===================
 - A patch is available to fix this vulnerability. Please read the 
   Security Bulletin at
   http://www.microsoft.com/technet/security/bulletin/ms01-048.asp
   for information on obtaining this patch.

Acknowledgment:
===============
 - Seiichi Tatsukawa of Rational Software (http://www.rational.com)

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