Microsoft Security Bulletin MS99-003
Patch Available for IIS "Malformed FTP List Request" Vulnerability
Patch Availability Information Updated: March 10, 2003
Originally Posted: February 3, 1999
Microsoft has released a patch that eliminates a vulnerability in the Internet Information Server FTP service. This vulnerability could allow denial of service attacks against the server or, under certain conditions, could allow arbitrary code to be executed on the server.
A fully supported fix for this problem is available. As detailed below in What Customers Should Do, Microsoft recommends that customers who are at risk from this vulnerability apply the patch.
The FTP service in IIS has an unchecked buffer in a component that processes "list" commands. This results in a vulnerability that poses two threats to safe operation. The first is a denial of service threat; a malformed "list" request could overflow the buffer causing the server to crash. The second is more esoteric and would be far more difficult to exploit. A carefully-constructed "list" request could cause arbitrary code to execute on the server via a classic buffer overrun technique. Neither variant could be exploited accidentally.
It is noteworthy that the "list" command is only available to users after they have authenticated to the server. As a result, only users who are authorized to use the server would be able to mount such an attack, and their presence on the server could be logged if the owner of the site chose to do so. However, many sites provide guest accounts, and this could allow a malicious user to attack the server anonymously.
Microsoft has no reports of any customers being affected by this vulnerability. However, Microsoft is proactively releasing a patch that corrects the problem.
Affected Software Versions
The following software versions are affected:
- Microsoft Internet Information Server 3.0 and 4.0
Vulnerability Identifier: CVE-1999-0349
What Microsoft is Doing
On February 3rd, Microsoft released a patch that fixes the problem identified above. This patch is available for download from the sites listed below.
Microsoft 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 188348, Specially-Malformed FTP Requests Can Create Denial of Service
(Note It might take 24 hours from the original posting of this bulletin for the KB article to be visible in the Web-based Knowledge Base.)
Microsoft has posted hot fixes to address this problem. Please note that all of these patches are designed to be applied atop Windows NT 4.0 SP4.
- Fix for X86 version of IIS 3.0:
- Fix for Alpha version of IIS 3.0:
- Fix for X86 version of IIS 4.0:
- Fix for Alpha version of IIS 4.0:
What customers should do
Microsoft highly recommends that all affected customers download the patch to protect their computers. The complete URL for each affected software version is provided above in What Microsoft is Doing.
Please see the following references for more information related to this issue.
- Microsoft Security Bulletin MS99-003, Patch Available for IIS "Malformed FTP List Request" Vulnerability (the Web-posted version of this bulletin), http://www.microsoft.com/technet/security/bulletin/ms99-003.mspx.
- Microsoft Knowledge Base (KB) article 188348, Specially-Malformed FTP Requests Can Create Denial of Service.
Microsoft wishes to acknowledge the eEye Digital Security Team for discovering this vulnerability.
Obtaining Support on this Issue
This is a supported patch. If you have problems installing this patch or require technical assistance with this patch, please contact Microsoft Technical Support. For information on contacting Microsoft Technical Support, please see http://support.microsoft.com/contactussupport/?ws=support.
- February 3, 1999: Bulletin Created
- 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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