Microsoft Distributed Transaction Controller Packet Relay DoS Vulnerability iDEFENSE Security Advisory 10.11.05 www.idefense.com/application/poi/display?id=319&type=vulnerabilities October 11, 2005 I. BACKGROUND The Distributed Transaction Controller provides a method for disparate processes to complete atomic transactions. The Transaction Internet Protocol (TIP) is one the ways that the DTC service can be accessed. This service is part of a standard installation on Windows NT 4.0, Windows 2000, Windows XP and Windows 2003. II. DESCRIPTION Remote exploitation of a denial of service vulnerability within various versions of Microsoft Corp.'s Windows operating system allows attackers to flood systems with connection attempts from legitimate MSDTC servers. The vulnerability specifically exists because of the functionality in the TIP protocol that allows a remote IP address and port number to be specified for a connection. The attack can be performed by connecting to the MSDTC server and providing an identifier that contains the IP address and port number to flood. After a specific sequence of commands, the attacker can force an error and cause the DTC service to connect to the target IP and port. The DTC service will continue to make connections to that host and port, one at a time, per stalled transaction. If the target host and port provides anything other than a certain set of response messages to the IDENTIFY request on the connection, the DTC service will disconnect and then reconnect to the service. The attacker can keep submitting new transactions to the DTC service, increasing the total number of connections made to the target. III. ANALYSIS Successful exploitation of this vulnerability could allow an attacker to proxy a denial of service attack through a MSDTC server that they do not otherwise have access to. An attacker could easily scan public IP ranges and find servers with TIP enabled and then force them to flood a target with repeated connections attempts. This attack can also be used to cause a DoS on the MSDTC server itself by specifying a loopback address with port 445. This service should not be exposed to public networks, thus mitigating the risk of this vulnerability. IV. DETECTION iDEFENSE has confirmed the existence and exploitability of this vulnerability in Microsoft Windows 2000 SP4. All versions of Microsoft Windows with the vulnerable service running are suspected vulnerable. V. WORKAROUND iDEFENSE is currently unaware of any workarounds for this issue. VI. VENDOR RESPONSE The vendor security advisory and appropriate patches are available at: http://www.microsoft.com/technet/security/Bulletin/MS05-051.mspx VII. CVE INFORMATION The Common Vulnerabilities and Exposures (CVE) project has assigned the name CAN-2005-1980 to this issue. This is a candidate for inclusion in the CVE list (http://cve.mitre.org), which standardizes names for security problems. VIII. DISCLOSURE TIMELINE 03/23/2005 Initial vendor notification 03/23/2005 Initial vendor response 10/11/2005 Coordinated public disclosure IX. CREDIT The discoverer of this vulnerability wishes to remain anonymous. Get paid for vulnerability research http://www.idefense.com/poi/teams/vcp.jsp Free tools, research and upcoming events http://labs.idefense.com X. LEGAL NOTICES Copyright (c) 2005 iDEFENSE, Inc. Permission is granted for the redistribution of this alert electronically. It may not be edited in any way without the express written consent of iDEFENSE. If you wish to reprint the whole or any part of this alert in any other medium other than electronically, please email customerservice@private for permission. Disclaimer: The information in the advisory is believed to be accurate at the time of publishing based on currently available information. Use of the information constitutes acceptance for use in an AS IS condition. There are no warranties with regard to this information. Neither the author nor the publisher accepts any liability for any direct, indirect, or consequential loss or damage arising from use of, or reliance on, this information.
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