Microsoft Security Bulletin MS99-058 - Critical
Patch Available for "Virtual Directory Naming" Vulnerability
Published: December 21, 1999
Originally Posted: December 21, 1999
Microsoft has released a patch that eliminates a vulnerability in Microsoft® Internet Information Server and other products that run atop it. Under certain conditions, the vulnerability could cause a web server to send the source code of .ASP and other files to a visiting user.
Frequently asked questions regarding this vulnerability can be found at http://www.microsoft.com/technet/security/bulletin/fq99-058.mspx.
If a file on one of the affected web server products resides in a virtual directory whose name contains a legal file extension, the normal server-side processing of the file can be bypassed. The vulnerability would manifest itself in different ways depending on the specific file type requested, the specific file extension in the virtual directory name, and the permissions that the requester has in the directory. In most cases, an error would result and the requested file would not be served. In the worse case, the source code of .ASP or other files could be sent to the browser.
This vulnerability would be most likely to occur due to administrator error, or if a product generated an affected virtual directory name by default. (Front Page Server Extensions is one such product). Recommended security practices militate against including sensitive information in .ASP and other files that require server-side processing, and if this recommendation is observed, there would be no sensitive information divulged even if this vulnerability occurred. In any event, an affected virtual directory could be identified during routine testing of the server.
Affected Software Versions
- Microsoft Internet Information Server 4.0
- Microsoft Site Server 3.0
- Microsoft Site Server Commerce Edition 3.0
NOTE: Additional security patches are available at the Microsoft Download Center
Please see the following references for more information related to this issue.
- Microsoft Security Bulletin MS99-058: Frequently Asked Questions, http://www.microsoft.com/technet/security/bulletin/fq99-058.mspx.
- Microsoft Knowledge Base (KB) article 238606, Page Contents Visible For Certain Virtual Directory Names, http://support.microsoft.com/default.aspx?scid=kb;en-us;238606&sd=tech.
(Note: It may take 24 hours from the original posting of this bulletin for this KB article to be visible.)
- Microsoft Knowledge Base (KB) article 186803, Browsing Folders with Script-Mapped Extensions Returns Errors, http://support.microsoft.com/default.aspx?scid=kb;en-us;186803&sd=tech.
- Microsoft 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.
Microsoft acknowledges Adam Hunger for bringing this issue to our attention.
- December 21, 1999: Bulletin Created.
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