__________________________________________________________ The U.S. Department of Energy Computer Incident Advisory Center ___ __ __ _ ___ / | /_\ / \___ __|__ / \ \___ __________________________________________________________ INFORMATION BULLETIN Unchecked Buffer in ISAPI Extension of IIS 5.0 Server May 2, 2001 21:00 GMT Number L-078 ______________________________________________________________________________ PROBLEM: The Microsoft IIS 5.0 web server running on Windows 2000 has a buffer overflow vulnerabilty which will give an attacker complete control of the server. PLATFORM: Microsoft IIS 5.0 running on Windows 2000 DAMAGE: A remote attacker can conduct a buffer overrun attack and cause code of their choice to run on the server. Such code would run in the Local System security context giving the attacker complete control of the server, and would enable them to take virtually any action they chose. SOLUTION: Apply the patch as shown in Microsoft Security Bulletin MS01-023. http://www.microsoft.com/technet/security/bulletin/MS01-023.asp ______________________________________________________________________________ VULNERABILITY The risk is HIGH, remote system level code execution ASSESSMENT: ______________________________________________________________________________ [***** Start Microsoft Security Bulletin *****] Title: Unchecked Buffer in ISAPI Extension Could Enable Compromise of IIS 5.0 Server Date: 01 May 2001 Software: Windows 2000 Server Windows 2000 Advanced Server Windows 2000 Datacenter Server Impact: Run code of attacker's choice, in Local System context Bulletin: MS01-023 Microsoft encourages customers to review the Security Bulletin at: http://www.microsoft.com/technet/security/bulletin/MS01-023.asp. - ---------------------------------------------------------------------- Issue: ====== Windows 2000 introduced native support for the Internet Printing Protocol (IPP), an industry-standard protocol for submitting and controlling print jobs over HTTP. The protocol is implemented in Windows 2000 via an ISAPI extension that is installed by default on all Windows 2000 servers but which can only be accessed via IIS 5.0. A security vulnerability results because the ISAPI extension contains an unchecked buffer in a section of code that handles input parameters. This could enable a remote attacker to conduct a buffer overrun attack and cause code of her choice to run on the server. Such code would run in the Local System security context. This would give the attacker complete control of the server, and would enable her to take virtually any action she chose. The attacker could exploit the vulnerability against any server with which she could conduct a web session. No other services would need to be available, and only port 80 (HTTP) or 443 (HTTPS) would need to be open. Clearly, this is a very serious vulnerability, and Microsoft strongly recommends that all IIS 5.0 administrators install the patch immediately. Alternatively, customers who cannot install the patch can protect their systems by removing the mapping for Internet Printing ISAPI extension. Mitigating Factors: ==================== - Servers on which the mapping for the Internet Printing ISAPI extension has been removed are not at risk from this vulnerability. The process for removing the mapping is discussed in the IIS 5.0 Security Checklist (http://www.microsoft.com/technet/security/iis5chk.asp). The High Security template provided in the checklist (http://www.microsoft.com/technet/security/tools.asp) removes the mapping, as does the Windows 2000 Internet Security Tool unless the user explicitly chose to retain Internet Printing. - The attacker's ability to extend her control from a compromised web server to other machines would be heavily dependent on the specific configuration of the network. Best practices recommend that the network architecture reflect the position of special risk occupied by network-edge machines like web servers and use measures like DMZs and limited domain memberships to isolate such machines from the rest of the network. Taking such measures would impede an attacker's ability to broaden the scope of the compromise. Patch Availability: =================== - A patch is available to fix this vulnerability. Please read the Security Bulletin http://www.microsoft.com/technet/security/bulletin/ms01-023.asp for information on obtaining this patch. Acknowledgment: =============== - eEye Digital Security (http://www.eeye.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 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/ (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-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 L-073: Microsoft ISA Web Proxy Service Denial of Service L-074: Microsoft WebDAV Runs Scripts As User L-075: FreeBSD IPFilter May Incorrectly Pass Packets L-076: Red Hat Ptrace and Exec Race Conditions l-077: The Glacier Backdoor