Vulnerability Note VU#412203

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

Overview

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

I. Description

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.

II. Impact

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.

III. Solution

Apply a patch as described in MS02-018.

Systems Affected

Vendor	Status	Date Updated
Microsoft	Vulnerable	10-Apr-2002

References

http://www.microsoft.com/technet/security/bulletin/MS02-018.asp

Credit

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

This document was written by Shawn V. Hernan.

Other Information

Date Public	04/10/2002
Date First Published	04/10/2002 05:09:25 PM
Date Last Updated	04/10/2002
CERT Advisory
CVE Name	CAN-2002-0073
US-CERT Technical Alerts
Metric	24.48
Document Revision	4

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