Microsoft Security Bulletin MS99-013
Patches Available for File Viewers Vulnerability
Patch Availability Information Updated: March 10, 2003
Originally Posted: May 7, 1999
Updated: May 19, 1999
This is an update to Microsoft Security Bulletin MS99-013. The purpose of the update is to advise customers of the availability of patches that eliminate a vulnerability that occurs in some file viewers included in Microsoft® Internet Information Server and Site Server. The vulnerability could allow a web site visitor to view, but not to change, files on the server, provided that they knew or guessed the name of each file and had access rights to it based on Windows NT ACLs.
Microsoft Site Server and Internet Information Server include tools that allow web site visitors to view selected files on the server. These are installed by default under Site Server, but must be explicitly installed under IIS. These tools are provided to allow users to view the source code of sample files as a learning exercise, and are not intended to be deployed on production web servers. The underlying problem in this vulnerability is that the tools do not restrict which files a web site visitor can view.
It is important to note several important points:
- These file viewers are not installed by default under IIS.
- The web site visitor would need to know or guess the name of each file they wished to view.
- This vulnerability only allows a web site visitor to view files, not to change them or to create new ones.
- The file viewers are subject to normal Windows NT file permission ACLs. A web site visitor could only use the file viewers to read files for which they have read access.
- The viewers can only be used to view files on the same disk partition as the currently-displayed web page. Databases such as those used by e-commerce servers are typically stored on a different physical drive, and these would not be at risk.
While there are no reports of customers being adversely affected by this vulnerability, Microsoft is proactively releasing this bulletin to allow customers to take appropriate action to protect themselves against it.
Affected Software Versions
- Microsoft Site Server 3.0, which is included with Microsoft Site Server 3.0 Commerce Edition, Microsoft Commercial Internet System 2.0, and Microsoft BackOffice Server 4.0 and 4.5
- Microsoft Internet Information Server 4.0
- ShowCode.asp Vulnerability: CAN-1999-0736
- ViewCode.asp Vulnerability: CAN-1999-0737
- Code.asp Vulnerability: CAN-1999-0738
- CodeBrws.asp Vulnerability: CAN-1999-0739
- Winmsdp.exe Vulnerability: CAN-1999-1451
What Microsoft is Doing
Microsoft has released patches that fix the problem identified. The patches are available for download from the sites listed below in What Customers Should Do.
Microsoft also has sent this security bulletin to customers subscribing to the Microsoft Product Security Notification Service. See The Microsoft Product Security Notification Service for more information about this free customer service.
Microsoft has published the following Knowledge Base (KB) article on this issue:
- Microsoft Knowledge Base (KB) article 231368, Solution Available for File Viewers Vulnerability, http://support.microsoft.com/default.aspx?scid=kb;en-us;231368&sd=tech.
- Microsoft Knowledge Base (KB) article 231656, Preventing Viewcode.asp from Viewing Known Server Files, http://support.microsoft.com/default.aspx?scid=kb;en-us;231656&sd=tech (Note It might take 24 hours from the posting of the bulletin for the updates to the KB articles to be visible in the Web-based Knowledge Base.)
What Customers Should Do
Microsoft highly recommends that customers evaluate the degree of risk that this vulnerability poses to their systems and determine whether to download and install the patch. The patch can be found at:
- Internet Information Server: http://www.microsoft.com/technet/security/patchavailability.mspx
- Site Server: http://www.microsoft.com/technet/security/patchavailability.mspx
Microsoft has provided a checklist that customers can use to ensure that their web servers have been properly secured. This checklist is available at http://www.microsoft.com/technet/security/chklist/iischk.mspx
Please see the following references for more information related to this issue.
- Microsoft Security Bulletin MS99-013, Solution Available for File Viewers Vulnerability (The Web-posted version of this bulletin), http://www.microsoft.com/technet/security/bulletin/ms99-013.mspx.
- Microsoft Knowledge Base (KB) article 231368, Patches Available for File Viewers Vulnerability http://support.microsoft.com/default.aspx?scid=kb;en-us;231368&sd=tech.
- Microsoft Knowledge Base (KB) article 231656, Preventing Viewcode.asp from Viewing Known Server Files http://support.microsoft.com/default.aspx?scid=kb;en-us;231656&sd=tech.
Obtaining Support on this Issue
If you require technical assistance with this issue, please contact Microsoft Technical Support. For information on contacting Microsoft Technical Support, please see http://support.microsoft.com/contactussupport/?ws=support.
Microsoft acknowledges WebTrends (http://www.webtrends.com) for discovering this vulnerability and reporting it to us.
- May 07, 1999: Bulletin Created.
- May 19, 1999: Bulletin updated to provide patch information.
- V2.0 (March 10, 2003): Introduced versioning and updated patch availability information.
For additional security-related information about Microsoft products, please visit http://www.microsoft.com/technet/security
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