Security Bulletin

Microsoft Security Bulletin MS99-054 - Critical

Patch Available for "WPAD Spoofing" Vulnerability

Published: December 01, 1999

Version: 1.0

Originally Posted: December 01, 1999

Summary

Microsoft has released a version upgrade that eliminates a vulnerability in Microsoft® Internet Explorer 5. Under very specific conditions, the vulnerability could allow a malicious user to provide proxy settings to web clients in another network.

Frequently asked questions regarding this vulnerability can be found at https://www.microsoft.com/technet/security/bulletins/fq99-054.mspx.

Issue

The IE 5 Web Proxy Auto-Discovery (WPAD) feature enables web clients to automatically detect proxy settings without user intervention. The algorithm used by WPAD prepends the hostname "wpad" to the fully-qualified domain name and progressively removes subdomains until it either finds a WPAD server answering the domain name or reaches the third-level domain. For instance, web clients in the domain a.b.microsoft.com would query wpad.a.b.microsoft, wpad.b.microsoft.com, then wpad.microsoft.com. A vulnerability arises because in international usage, the third-level domain may not be trusted. A malicious user could set up a WPAD server and serve proxy configuration commands of his or her choice.

Affected Software Versions

  • Microsoft Internet Explorer 5

Vulnerability Identifier: CVE-1999-0858

Patch Availability

The vulnerability is eliminated by IE 5.01, which is available at:

More Information

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

Obtaining Support on this Issue

This is a fully supported patch. Information on contacting Microsoft Technical Support is available at </https:>https:.

Acknowledgments

Microsoft acknowledges Tim Adam of Open Software Associates for bringing this issue to our attention.

Revisions

  • December 01, 1999: 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.

Built at 2014-04-18T13:49:36Z-07:00 </https:>