Rpcss.exe Consumes 100% CPU Due to RPC Spoofing Attack (193233)
The information in this article applies to:
- Microsoft Windows NT Server 4.0 Terminal Server Edition
- Microsoft Windows NT Workstation 4.0
- Microsoft Windows NT Server 4.0
This article was previously published under Q193233 SYMPTOMS
System and network performance could degrade and the Rpcss.exe process
could consume 100 percent of CPU time. Analyzing the network with a
protocol analyzer shows multiple RPC REJECT packets (addressed to UDP port
135) between two or more systems because of an RPC spoofing attack.
CAUSE
This problem is caused by a malicious attack on the remote procedure call
(RPC) components in Windows NT.
A UDP packet with a destination port of 135 can be spoofed so that it
appears as if one datagram RPC server sent bad data to another datagram RPC
server. The second server returns a REJECT packet. The first server replies
with another REJECT packet creating a loop that is not broken until a
packet is dropped. If this spoofed UDP packet is sent to multiple
computers, an infinite loop may be created, consuming processor resources
and network bandwidth.
RESOLUTIONWindows NT 4.0
To resolve this problem, obtain the latest service pack for Windows NT
version 4.0. For more information, please see the following article in the
Microsoft Knowledge Base.
152734
How To Obtain the Latest Windows NT 4.0 Service Pack
This hotfix has been posted as Snk-fixi.exe and Snk-fixa.exe. For your
convenience, the English version of this post-SP3 hotfix has been posted to
the following Internet location. However, Microsoft recommends that you
install Windows NT 4.0 Service Pack 4 to correct this problem.
Windows NT 4.0, Terminal Server EditionTo resolve this problem, obtain the latest service pack for Windows NT Server 4.0, Terminal Server Edition. For additional information, click the following article number to view the article in the
Microsoft Knowledge Base:
152734 How to Obtain the Latest Windows NT 4.0 Service Pack
This hotfix has been posted to the following Internet location as
Snk-fixi.exe and Snk-fixa.exe:
STATUS
Microsoft has confirmed this problem could result in some degree of
security vulnerability in Windows NT version 4.0 and Windows NT 4.0,
Terminal Server Edition.
This problem was first corrected in Windows NT 4.0 Service Pack 4.0 and Windows NT Server 4.0, Terminal Server Edition Service Pack 4.
| Modification Type: | Major | Last Reviewed: | 4/20/2006 |
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| Keywords: | kbbug kbfix KB193233 |
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