Microsoft Security Bulletin MS99-039 - Critical
Patch Available for "Domain Resolution" and "FTP Download" Vulnerabilities
Published: September 23, 1999 | Updated: March 21, 2003
Patch Availability Information Updated: March 21, 2003
Originally Posted: September 23, 1999
Revised: September 30, 1999
Microsoft has released a patch that eliminates two security vulnerabilities in Microsoft® Internet Information Server (IIS) 4.0 and Microsoft Commercial Internet System (MCIS) 2.5. The vulnerabilities allow security restrictions in IIS and MCIS to be bypassed under certain conditions, as discussed below. Frequently asked questions regarding this vulnerability can be found at /technet/security/bulletin/fq99-039.mspx.
There are two vulnerabilities at issue here:
- IIS 4.0 provides the ability to restrict access to a web site based on the user's domain. However, if IIS cannot resolve a user's IP address to a domain, it will grant the user's first request for a session. It will correctly deny them thereafter. This vulnerability affects IIS 4.0 only; it does not any other Microsoft product, including MCIS.
- A user who accesses an FTP site via a browser will be able to download files even if they are marked No Access. This vulnerability is due to a regression error that was introduced in hotfixes released after Windows NT 4.0 Service Pack 5; it does not exist in SP5 or in previous versions. This vulnerability affects both IIS 4.0 and MCIS 2.5, but no other Microsoft products.
Neither vulnerability provides a means to usurp control of the server. A patch is available that eliminates both vulnerabilities.
Affected Software Versions
- Microsoft Internet Information Server 4.0
- Microsoft Commercial Internet System 2.5
- IIS 4.0: http://www.microsoft.com/technet/security/patchavailability.mspx
- MCIS 2.5: http://www.microsoft.com/technet/security/patchavailability.mspx
Please see the following references for more information related to this issue.
- Microsoft Security Bulletin MS99-039: Frequently Asked Questions, http://www.microsoft.com/technet/security/bulletin/fq99-039.mspx.
- Microsoft Knowledge Base (KB) article 241805, Combined FTP and Domain Restriction Security Patch for IIS 4.0, http://support.microsoft.com/default.aspx?scid=kb;en-us;241805&sd=tech.
- Microsoft Knowledge Base (KB) article 241562, Denying Access With Domain Name Restriction Still Allows Unresolved Clients, http://support.microsoft.com/default.aspx?scid=kb;en-us;241562&sd=tech.
- Microsoft Knowledge Base (KB) article 241407, Files can be downloaded from an FTP Server when the file permissions are explicitly No Access, http://support.microsoft.com/default.aspx?scid=kb;en-us;241407&sd=tech.
- Microsoft Knowledge Base (KB) article 242559, FTP Allows read on a file with NTFS permissions of No Access, http://support.microsoft.com/default.aspx?scid=kb;en-us;242559&sd=tech.
- Microsoft Security web site, /technet/security/default.mspx.
Note It may take 24 hours from the original posting of this bulletin for the KB articles to be visible.
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 Rich Harrison of Halliburton Company for discovering the "Domain Resolution" vulnerability and reporting it to us. Microsoft acknowledges Roberto Franceschetti for discovering the FTP Access vulnerability and bringing it to our attention.
- September 23, 1999: Bulletin Created.
- September 30, 1999: Bulletin modified to include information regarding MCIS association with this vulnerability.
- V2.0 (March 21, 2003): Introduced versioning and updated patch availability information.
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