CERT-SEI

Multiple Vulnerabilities in Microsoft IIS

Original release date: April 11, 2002
Last revised: --
Source: CERT/CC

A complete revision history can be found at the end of this file.

Systems Affected

  • Microsoft IIS 4.0, 5.0, and 5.1

Overview

A variety of vulnerabilities exist in various versions of Microsoft IIS. Some of these vulnerabilities may allow an intruder to execute arbitrary code on vulnerable systems.

I. Description

There are a variety of vulnerabilities in Microsoft IIS. Many of these vulnerabilities are buffer overflows that could permit an intruder to execute arbitrary code on vulnerable systems.

We strongly encourage all sites running IIS to read Microsoft's advisory on these and other vulnerabilities and take appropriate action as soon as practical. Microsoft's bulletin is available at
http://www.microsoft.com/technet/security/bulletin/MS02-018.asp

Additional information about these vulnerabilities is available at

Vulnerability note
CVE number
Title
http://www.kb.cert.org/vuls/id/363715 CAN-2002-0071 Microsoft Internet Information Server (IIS) vulnerable to heap overflow during processing of crafted ".htr" request by "ISM.DLL" ISAPI filter
http://www.kb.cert.org/vuls/id/883091 CAN-2002-0074 Microsoft Internet Information Server (IIS) contains cross-site scripting vulnerability in IIS Help Files search facility
http://www.kb.cert.org/vuls/id/886699 CAN-2002-0148 Microsoft Internet Information Server (IIS) contains cross-site scripting vulnerability in HTTP error page results
http://www.kb.cert.org/vuls/id/520707 CAN-2002-0075 Microsoft Internet Information Server (IIS) contains cross-site scripting vulnerability in redirect response messages
http://www.kb.cert.org/vuls/id/412203 CAN-2002-0073 Microsoft Internet Information Server (IIS) vulnerable to DoS via malformed FTP connection status request
http://www.kb.cert.org/vuls/id/454091 CAN-2002-0150 Microsoft Internet Information Server (IIS) vulnerable to buffer overflow via inaccurate checking of delimiters in HTTP header fields
http://www.kb.cert.org/vuls/id/721963 CAN-2002-0149 Microsoft Internet Information Server (IIS) buffer overflow in server-side includes (SSI) containing long invalid file name
http://www.kb.cert.org/vuls/id/521059 CAN-2002-0072 Microsoft Internet Information Server (IIS) vulnerable to DoS when URL request exceeds maximum allowed length
http://www.kb.cert.org/vuls/id/610291 CAN-2002-0079 Microsoft Internet Information Server (IIS) buffer overflow in chunked encoding transfer mechanism
http://www.kb.cert.org/vuls/id/669779 CAN-2002-0147 Microsoft Internet Information Server (IIS) buffer overflow in chunked encoding transfer mechanism

II. Impact

For many of the vulnerabilities, an intruder could execute arbitrary code with privileges that vary according to which version of IIS is running. In general, IIS 4.0 permits an intruder to execute code with complete administrative privileges, while IIS 5.0 and 5.1 permit an intruder to execute code with the privileges of the IWAM_computername account.

III. Solution

Microsoft Corporation has released Microsoft Security Bulletin MS02-018, which announces the availability of a cumulative patch to address a variety of problems. We strongly encourage you to read this bulletin and take the appropriate corrective measures. MS02-018 is available at

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

In addition to applying the patch, or until it can be applied, we recommend the following actions:

  • Use the IIS Lockdown tool and URLScan to eliminate or reduce the impact of some of these vulnerabilites; they may also eliminate or reduce other vulnerabilities that have not yet been discovered. The IIS Lockdown tool can also be used to disable ASP if it's not needed. More information about the IIS Lockdown tool and URLScan can be found at
    http://www.microsoft.com/technet/security/tools/locktool.asp
    http://www.microsoft.com/technet/security/URLScan.asp
  • As Microsoft has recommended for quite some time, disable the HTR ISAPI extension unless it is absolutely required.
  • Disable anonymous FTP unless it is required.
  • Don't give login credentials on IIS servers to untrusted users.

Our thanks to Microsoft Corporation for the information contained in their advisory. Additionally, our thanks go to the various individuals and organizations whom Microsoft identified as discovering the vulnerabilities, including eEye Digital Security (http://www.eeye.com), Serge Mister of Entrust, Inc. (http://www.entrust.com), Dave Aitel of @Stake (http://www.atstake.com), Peter Grundl of KPMG, Joe Smith (jsm1th@hotmail.com) and zenomorph (admin@cgisecurity.com) of http://www.cgisecurity.com, Keigo Yamazaki of the LAC SNS Team (http://www.lac.co.jp/security/), and Thor Larholm of Jubii A/S.


Author: Shawn V. Hernan

Copyright 2002 Carnegie Mellon University.

Revision History

April 11, 2002:  Initial release