Vulnerability Note VU#412203

Microsoft Internet Information Server (IIS) vulnerable to DoS via malformed FTP connection status request

Original Release date: 10 Apr 2002 | Last revised: 10 Apr 2002


A vulnerability in IIS could allow an intruder to disrupt ordinary operations of both FTP and Web services on vulnerable IIS servers.


IIS includes an FTP server. An intruder who sends a malformed request for the status of an existing connection could cause the IIS server to fail, resulting in the loss of both FTP service and HTTP service. In order to be able to issue the status request, an intruder needs an existing FTP session, which means he either has to have login credentials or anonymous FTP access to a vulnerable system. (Theoretically, an intruder may also be able to exploit this vulnerability by injecting data into an existing FTP session through ISN prediction or other techniques. ) For more information, see Microsoft Security Bulletin MS02-018.


Intruders can halt the operation of vulnerable IIS servers. On IIS 5.0 and IIS 5.1, IIS will automatically restart, though the intruder may be able to repeat the attack indefinitely. On IIS 4.0, IIS has to be manually restarted.


Apply a patch as described in MS02-018.

Systems Affected (Learn More)

VendorStatusDate NotifiedDate Updated
MicrosoftAffected-10 Apr 2002
If you are a vendor and your product is affected, let us know.

CVSS Metrics (Learn More)

Group Score Vector
Base N/A N/A
Temporal N/A N/A
Environmental N/A N/A



Our thanks to Microsoft Corporation, upon whose advisory this document is based.

This document was written by Shawn V. Hernan.

Other Information

  • CVE IDs: CAN-2002-0073
  • Date Public: 10 Apr 2002
  • Date First Published: 10 Apr 2002
  • Date Last Updated: 10 Apr 2002
  • Severity Metric: 24.48
  • Document Revision: 4


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