-----BEGIN PGP SIGNED MESSAGE----- __________________________________________________________ The U.S. Department of Energy Computer Incident Advisory Center ___ __ __ _ ___ / | /_\ / \___ __|__ / \ \___ __________________________________________________________ INFORMATION BULLETIN Microsoft ISA Web Proxy Service Denial of Service [Microsoft Bulletin MS01-021] April 20, 2001 00:00 GMT Number L-073 ______________________________________________________________________________ PROBLEM: The ISA server web proxy service does not correctly handle web requests that contain a particular type of malformed argument. Processing such a request would cause the web proxy service to fail, blocking all incoming and outgoing requests until the service is restarted. PLATFORM: Microsoft ISA Server 2000 DAMAGE: Crashing the web proxy service would block all incoming and outgoing requests creating a denial of service condition. SOLUTION: Apply the patch as shown in Microsoft Security Bulletin MS01-021. http://www.microsoft.com/technet/security/bulletin/MS01-021.asp. ______________________________________________________________________________ VULNERABILITY The risk is LOW. Restarting the web proxy service clears the ASSESSMENT: blockage. The vulnerability cannot allow an intruder to breach security. The blockage does not disrupt any other services on the ISA server. ______________________________________________________________________________ [***** Start Microsoft Security Bulletin *****] - - ----------------------------------------------------------------------- Title: Invalid Web Request Can Cause Access Violation in ISA Server Web Proxy Service Date: 16 April 2001 Software: ISA Server 2000 Impact: Denial of service Bulletin: MS01-021 Microsoft encourages customers to review the Security Bulletin at: http://www.microsoft.com/technet/security/bulletin/MS01-021.asp. - - ----------------------------------------------------------------------- Issue: ====== The ISA Server Web Proxy service does not correctly handle web requests that contain a particular type of malformed argument. Processing such a request would result in an access violation, which would cause the Web Proxy service to fail. This would disrupt all ingoing and outgoing web proxy requests until the service was restarted. Mitigating Factors: ==================== - The vulnerability could be exploited from the Internet only if the Web Publishing feature were enabled. By default, this feature is disabled. - The vulnerability would not enable an attacker to breach the security of the firewall - that is, it would not enable the attacker to access protected resources or bypass the firewall. It would only enable the attacker to deny legitimate service to other users. - The vulnerability would only allow the Web Proxy service to be disrupted. Other ISA services would continue functioning normally. Patch Availability: =================== - A patch is available to fix this vulnerability. Please read Security Bulletin http://www.microsoft.com/technet/security/bulletin/ms01-021.asp for information on obtaining this patch. Acknowledgment: =============== - Dr. Richard Reiner, Graham Wiseman, Matthew Siemens, and Kent Nicolson of FSC Internet Corp. / SecureXpert Labs (http://www.fscinternet.com / http://www.securexpert.com) - - ---------------------------------------------------------------------- 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 *****] ______________________________________________________________________________ CIAC wishes to acknowledge the contributions of Microsoft for the information contained in this bulletin. ______________________________________________________________________________ CIAC, the Computer Incident Advisory Capability, 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/ (or http://ciac.llnl.gov -- they're the same machine) Anonymous FTP: ftp.ciac.org (or ciac.llnl.gov -- they're the same machine) 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. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or the University of California, and shall not be used for advertising or product endorsement purposes. LAST 10 CIAC BULLETINS ISSUED (Previous bulletins available from CIAC) L-063: RedHat Linux Log Code Buffer Overflow/Unguarded Browser Call l-064: The Lion Internet Worm DDOS Risk L-065: Solaris Exploitation of snmpXdmid L-066: Internet Explorer MIME Mime Header Vulnerability L-067: Linux worm Adore L-068: Cisco VPN3000 Concentrator TELNET Vulnerability L-069: Cisco Content Services Switch User Account Vulnerability L-070: FTP Filename Expansion Vulnerability L-071: Various Vendors' Network Time Protocol (NTP) Vulnerability L-072: Cisco Catalyst 5000 Series 802.1x Vulnerability -----BEGIN PGP SIGNATURE----- Version: PGP for Business Security 5.5.2 iQCVAwUBOuCmALnzJzdsy3QZAQHyYAQAoIHT+AMOqeJy3SCbLVcMaiKjajjnRTgD RxwU//ckjB2D5ejxzCcVQ5/5DnQJbuKSbtLTjb4pe9a1MWZz4egrn5Dzyn50fYvW xHuZMT3lgQIJXPp9PQ67N1a8zSBoRTB3S60eLLL3iHPMVMWNp+dojx+yWnNi0arX 8q50Tv57qb4= =Ilvv -----END PGP SIGNATURE-----