Microsoft Security Bulletin (MS00-063)
Patch Available for "Invalid URL" Vulnerability
Originally posted: September 05, 2000
Microsoft has released a patch that eliminates a security
vulnerability in Microsoft(r) Internet Information Server (IIS). The
vulnerability could enable a malicious user to prevent an affected
web server from providing useful service.
Frequently asked questions regarding this vulnerability and the patch
can be found at
If an affected web server received a particular type of invalid URL,
it could, under certain conditions, start a chain of events that
would culminate in an invalid memory request that would cause the IIS
service to fail. This would prevent the server from providing web
This vulnerability does not provide the opportunity to compromise any
data on the server or to usurp any administrative privileges on the
server. An affected machine could be put back into service by
restarting the IIS service.
Although the effect of the vulnerability manifests itself through
IIS, the underlying problem actually lies within Windows NT 4.0.
Microsoft engineers worked extensively to identify scenarios for
exploiting the vulnerability directly through Windows NT 4.0, but did
not find any - the only scenarios identified to date involve IIS.
Nevertheless, it is possible that scenarios for exploiting the
vulnerability through Windows NT 4.0 do exist, and as a result, we
recommend that customers using Windows NT 4.0 consider applying the
Affected Software Versions
- Microsoft Internet Information Server 4.0
Note: As noted above in "Issue", the root cause of this vulnerability
lies in Windows NT 4.0, and Microsoft recommends that customers
using Windows NT 4.0 consider applying the patch.
- Microsoft Windows NT 4.0 Workstation, Server and Server,
- Microsoft Windows NT 4.0 Server, Terminal Server Edition: To be
Note Additional security patches are available at the Microsoft
Please see the following references for more information related to
- Frequently Asked Questions: Microsoft Security Bulletin MS00-063,
- Microsoft Knowledge Base article Q271652 discusses this issue
and will be available soon.
- Microsoft TechNet Security web site,
Obtaining Support on this Issue
This is a fully supported patch. Information on contacting Microsoft
Product Support Services is available at
Microsoft thanks Peter Grundl of VIGILANTe (http://www.vigilante.com)
for reporting this issue to us and working with us to protect
- September 05, 2000: Bulletin Created.
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Last Updated September 05, 2000