Microsoft Security Bulletin (MS00-054)

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Patch Available for "Malformed IPX Ping Packet" Vulnerability

Date Published: August 03, 2000

Summary

Microsoft has released a patch that eliminates a security
vulnerability in Microsoft(r) Windows 95, 98 and 98 Second Edition.
The vulnerability could be used to cause an affected system to fail,
and depending on the number of affected machines on a network,
potentially could be used to flood the network with superfluous
data. The affected system component generally is present only if it
has been deliberately installed.

Frequently asked questions regarding this vulnerability and
the patch can be found at
http://www.microsoft.com/technet/security/bulletin/fq00-054.asp

Issue

The Microsoft IPX/SPX protocol implementation (NWLink) supports the
IPX Ping command via the diagnostic port 0x456. Because of a flaw in
the implementation of the protocol in Windows 95, Windows 98 and
Windows 98 Second Edition, NWLink in these systems will respond to
an IPX ping packet even when the source network address has been
purposely modified to a broadcast address. This would give a
malicious user an opportunity to launch an attack by broadcasting a
single ping request - each affected machine that received the ping
would respond to it, potentially resulting in a broadcast storm. In
a large network, this could temporarily swamp the network's
bandwidth. In addition, upon seeing its own response, each affected
machine would attempt to process it, triggering a scenario that
would culminate in the machine's failure. A machine that failed due
to this vulnerability could be put back into service by rebooting.

IPX is not installed by default in Windows 98 and 98 Second Edition,
and is only installed by default in Windows 95 if there is a network
card present in the machine at installation time. Even when IPX is
installed, a malicious user's ability to exploit this vulnerability
would depend on whether he could deliver a Ping packet to an affected
machine. Routers frequently are configured to drop IPX packets, and
if such a router lay between the malicious user and an affected
machine, he could not attack it. Routers on the Internet, as a rule,
do not forward IPX packets, and this would tend to protect intranets
from outside attack, as well as protecting machines connected to the
Internet via dial-up connections. As discussed in the FAQ, the most
likely scenario in which this vulnerability could be exploited would
be one in which a malicious user on an intranet would attack
affected machines on the same intranet, or one in which a malicious
user on the Internet attacked affected machines on on his cable
modem or DSL subnet.

Affected Software Versions

• Microsoft Windows 95
• Microsoft Windows 98
• Microsoft Windows 98 Second Edition

Patch Availability

• Microsoft Windows 95:
  http://download.microsoft.com/download/win95/Update/8982/
  W95/EN-US/265334US5.EXE
• Microsoft Windows 98 and Windows 98 Second Edition:
  http://download.microsoft.com/download/win98/Update/8982/
  W98/EN-US/265334USA8.EXE

Note: Line breaks have been inserted into the URLs above for
readability.

Note: Additional security patches are available at the Microsoft
Download Center

More Information

Please see the following references for more information related to
this issue.

• Frequently Asked Questions: Microsoft Security Bulletin MS00-054,
  http://www.microsoft.com/technet/security/bulletin/fq00-054.asp
• Microsoft Knowledge Base article Q265334 discusses this issue and
  will be available soon.
• Microsoft TechNet Security web site,
  http://www.microsoft.com/technet/security/default.asp

Obtaining Support on this Issue

This is a fully supported patch. Information on contacting
Microsoft Technical Support is available at
http://support.microsoft.com/support/contact/default.asp.

Revisions

• August 03, 2000: Bulletin Created.

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Last Updated August 03, 2000