TechNet Home > TechNet Security > Bulletins

Microsoft Security Bulletin (MS00-023)

Patch Available for "Myriad Escaped Characters" Vulnerability

Originally Posted: April 12, 2000

Summary

Microsoft has released a patch that eliminates a security vulnerability in Microsoft® Internet Information Server. The vulnerability could allow a malicious user to slow a web server's response or prevent it from providing service altogether for a period of time.

Frequently asked questions regarding this vulnerability and the patch can be found at http://www.microsoft.com/technet/security/bulletin/fq00-023.mspx

Top of section

General Information

Issue

Special characters can be embedded in URLs by use of so-called escaped character sequences. By providing a specially-malformed URL with an extremely large number of escaped characters, a malicious user could arbitrarily increase the work factor associated with parsing the escaped characters, thereby consuming much or all of the CPU availability on the server and preventing useful work from being done.

The vulnerability does not provide any capability to cause the server to fail, or to add, change or delete data on it. The slowdown would only last until the URL had been processed, at which point service would return to normal.

Affected Software Versions

•	Microsoft Internet Information Server 4.0
•	Microsoft Internet Information Server 5.0

Vulnerability Identifier: CVE-2000-0258

Top of section

Patch Availability

•

Internet Information Server 4.0

http://www.microsoft.com/downloads/details.aspx?FamilyId=75F808BE-31DA-4B17-8071-C0A6A0284193&displaylang=en

•

Internet Information Server 5.0

http://www.microsoft.com/downloads/details.aspx?FamilyId=EEA91314-99A1-4393-AABC-DAB10DFABD3D&displaylang=en

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

Top of section

More Information

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

•	Frequently Asked Questions: Microsoft Security Bulletin MS00-023, http://www.microsoft.com/technet/security/bulletin/fq00-023.mspx
•	Microsoft Knowledge Base (KB) article 254142, Sending a large escaped character sequence can cause 100% CPU Usage http://support.microsoft.com/default.aspx?scid=kb;en-us;254142
•	Microsoft TechNet Security web site, http://www.microsoft.com/technet/security/default.mspx

Obtaining Support on this Issue

This is a fully supported patch. Information on contacting Microsoft Technical Support is available at http://support.microsoft.com/contactussupport/?ws=support.

Acknowledgments

Microsoft thanks Vanja Hrustic of the Relay Group for reporting the "Myriad Escaped Character" vulnerability to us and working with us to protect customers.

Revisions

•	April 12, 2000: Bulletin Created.

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.

Top of section

Top of page