CERT Advisory CA-2002-09 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 http://www.kb.cert.org/vuls VU#363715 CAN-2002-0071 Microsoft Internet Information Server (IIS) vulnerable to heap overflow during processing of crafted ".htr" request by "ISM.DLL" ISAPI filter VU#883091 CAN-2002-0074 Microsoft Internet Information Server (IIS) contains cross-site scripting vulnerability in IIS Help Files search facility VU#886699 CAN-2002-0148 Microsoft Internet Information Server (IIS) contains cross-site scripting vulnerability in HTTP error page results VU#520707 CAN-2002-0075 Microsoft Internet Information Server (IIS) contains cross-site scripting vulnerability in redirect response messages VU#412203 CAN-2002-0073 Microsoft Internet Information Server (IIS) vulnerable to DoS via malformed FTP connection status request VU#454091 CAN-2002-0150 Microsoft Internet Information Server (IIS) vulnerable to buffer overflow via inaccurate checking of delimiters in HTTP header fields VU#721963 CAN-2002-0149 Microsoft Internet Information Server (IIS) buffer overflow in server-side includes (SSI) containing long invalid file name VU#521059 CAN-2002-0072 Microsoft Internet Information Server (IIS) vulnerable to DoS when URL request exceeds maximum allowed length VU#610291 CAN-2002-0079 Microsoft Internet Information Server (IIS) buffer overflow in chunked encoding transfer mechanism VU#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@xxxxxxxxxxx) and zenomorph (admin@xxxxxxxxxxxxxxx) 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 Angel A. List admin. angel.alexander@xxxxxxxxx