. Department of Energy Computer Incident Advisory Center ___ __ __ _ ___ / | /_\ / \___ __|__ / \ \___ __________________________________________________________ INFORMATION BULLETIN Microsoft Cumulative Patch for IIS August 16, 2001 21:00 GMT Number L-132 ______________________________________________________________________________ PROBLEM: Microsoft has released a cumulative patch to fix five vulnerabilities resulting in either denial of service or elevation of privileges. This patch includes the functionality of all security patches to date for IIS 5.0, and for IIS 4.0 since Windows NT(r) 4.0 service Pack 5. PLATFORM: IIS 4.0 and 5.0 DAMAGE: Unpatched systems are vulnerable to denial of service attacks or the possibility of privileges being elevated. SOLUTION: Before applying the patch, system administrators should check the caveats discussed in this advisory. ______________________________________________________________________________ VULNERABILITY The risk is MEDIUM. This patch also eliminates the side effect ASSESSMENT: of the previous IIS cumulative patch by restoring proper functioning of UPN-style logons via FTP and W3SVC. ______________________________________________________________________________ [****** Start Microsoft Security Bulletin MS01-044 ******] ----------------------------------------------------------------------- Title: 15 August 2001 Cumulative Patch for IIS Date: 15 August 2001 Software: IIS 4.0 and 5.0 Impact: Five vulnerabilities resulting in either denial of service or privilege elevation Bulletin: MS01-044 Microsoft encourages customers to review the Security Bulletin at: http://www.microsoft.com/technet/security/bulletin/MS01-044.asp. ----------------------------------------------------------------------- Issue: ====== This patch is a cumulative patch that includes the functionality of all security patches released to date for IIS 5.0, and all patches released for IIS 4.0 since Windows NT(r) 4.0 Service Pack 5. A complete listing of the patches superseded by this patch is provided below, in the section titled "Additional information about this patch". Before applying the patch, system administrators should take note of the caveats discussed in the same section. In addition to including all previously released security patches, this patch also includes fixes for five newly discovered security vulnerabilities affecting IIS 4.0 and 5.0: - A denial of service vulnerability that could enable an attacker to cause the IIS 4.0 service to fail, if URL redirection has been enabled. The "Code Red" worm generates traffic that can in some cases exploit this vulnerability, with the result that an IIS 4.0 machine that wasn't susceptible to infection via the worm could nevertheless have its service disrupted by the worm. - A denial of service vulnerability that could enable an attacker to temporarily disrupt service on an IIS 5.0 web server. WebDAV doesn't correctly handle particular type of very long, invalid request. Such a request would cause the IIS 5.0 service to fail; by default, it would automatically restart. - A denial of service vulnerability involving the way IIS 5.0 interprets content containing a particular type of invalid MIME header. If an attacker placed content containing such a defect onto a server and then requested it, the IIS 5.0 service would be unable to serve any content until a spurious entry was removed from the File Type table for the site. - A buffer overrun vulnerability involving the code that performs server-side include (SSI) directives. An attacker who had the ability to place content onto a server could include a malformed SSI directive that, when the content was processed, would result in code of the attacker's choice running in Local System context. - A privilege elevation vulnerability that results because of a flaw in a table that IIS 5.0 consults when determining whether a process should in-process or out-of-process. IIS 5.0 contains a table that lists the system files that should always run in-process. However, the list provides the files using relative as well as Absolute addressing, with the result that any file whose name matched that of a file on the list would run in-process. In addition, this patch eliminates a side effect of the previous IIS cumulative patch (discussed in the Caveats section of Microsoft Security Bulletin MS01-026) by restoring proper functioning of UPN-style logons via FTP and W3SVC. Mitigating Factors: ==================== URL Redirection denial of service: - This vulnerability only affects IIS 4.0. IIS 5.0 is not affected. - The vulnerability only occurs if URL redirection is enabled. - The vulnerability does not provide any capability to compromise data on the server or gain administrative control over it. WebDAV request denial of service: - The vulnerability only affects IIS 5.0. IIS 4.0 is not affected. - The effect of an attack via this vulnerability would be temporary. The server would automatically resume normal service as soon as the malformed requests stopped arriving. - The vulnerability does not provide an attacker with any capability to carry out WebDAV requests. - The vulnerability does not provide any capability to compromise data on the server or gain administrative control over it. MIME header denial of service: - The vulnerability only affects IIS 5.0. IIS 4.0 is not affected. - In order to exploit this vulnerability, the attacker would need to have the ability to install content on the server. However, by default, unprivileged users do not have this capability, and best practices strongly recommend against granting it to untrusted users. SSI privilege elevation vulnerability: - In order to exploit this vulnerability, the attacker would need to have the ability to install content on the server. However, by default, unprivileged users do not have this capability, and best practices strongly recommend against granting it to untrusted users. System file listing privilege elevation vulnerability: - The vulnerability only affects IIS 5.0. IIS 4.0 is not affected. - In order to exploit this vulnerability, the attacker would need to have the ability to install content on the server. However, by default, unprivileged users do not have this capability, and best practices strongly recommend against granting it to untrusted users. Patch Availability: =================== - A patch is available to fix these vulnerabilities. Please read the Security Bulletin http://www.microsoft.com/technet/security/bulletin/ms01-044.asp for information on obtaining this patch. Acknowledgment: =============== - John Waters of Deloitte and Touche for reporting the MIME type denial of service vulnerability. - The NSFocus Security Team (http://www.nsfocus.com) for reporting the SSI privilege elevation vulnerability. - Oded Horovitz of Entercept(tm) Security Technologies (http://www.entercept.com) for reporting the system file listing privilege elevation vulnerability. ---------------------------------------------------------------------- THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY. [****** End Microsoft Security Bulletin MS01-044 ******] ______________________________________________________________________________ CIAC wishes to acknowledge the contributions of Microsoft for the information contained in this bulletin. ______________________________________________________________________________ CIAC, the Computer Incident Advisory Center, is the computer security incident response team for the U.S. Department of Energy (DOE) and the emergency backup response team for the National Institutes of Health (NIH). CIAC is located at the Lawrence Livermore National Laboratory in Livermore, California. CIAC is also a founding member of FIRST, the Forum of Incident Response and Security Teams, a global organization established to foster cooperation and coordination among computer security teams worldwide. CIAC services are available to DOE, DOE contractors, and the NIH. CIAC can be contacted at: Voice: +1 925-422-8193 (7x24) FAX: +1 925-423-8002 STU-III: +1 925-423-2604 E-mail: ciac@ciac.org Previous CIAC notices, anti-virus software, and other information are available from the CIAC Computer Security Archive. World Wide Web: http://www.ciac.org/ Anonymous FTP: ftp.ciac.org PLEASE NOTE: Many users outside of the DOE, ESnet, and NIH computing communities receive CIAC bulletins. If you are not part of these communities, please contact your agency's response team to report incidents. Your agency's team will coordinate with CIAC. The Forum of Incident Response and Security Teams (FIRST) is a world-wide organization. A list of FIRST member organizations and their constituencies can be obtained via WWW at http://www.first.org/. This document was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor the University of California nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial products, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation or favoring by the United States Government or the University of California. 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