Date: Mon, 15 Mar 1999 21:55:24 -0500 (EST) From: X-Force To: alert@iss.net Cc: X-Force Subject: ISSalert: ISS Security Advisory: LDAP Buffer overflow against Microsoft Directory Services TO UNSUBSCRIBE: email "unsubscribe alert" in the body of your message to majordomo@iss.net Contact alert-owner@iss.net for help with any problems! --------------------------------------------------------------------------- -----BEGIN PGP SIGNED MESSAGE----- ISS Security Advisory March 15, 1999 LDAP Buffer overflow against Microsoft Directory Services Synopsis: ISS X-Force has discovered a buffer overflow exploit against Microsoft Exchange's LDAP (Lightweight Directory Access Protocol) server which allows read access to the Exchange server directory by using an LDAP client. This buffer overflow consists of a malformed bind request that overflows the buffer and can execute arbitrary code. This attack can also cause the Exchange LDAP service to crash. This vulnerability exists in Microsoft Exchange Server version 5.5. Description: This exploit occurs during the LDAP binding process. Binding involves logging in or authenticating to a directory, and consists of sending a username, a password, and a binding method. There are two methods in which to use this vulnerablility against an Exchange server. The first consists of sending a particular type of invalid LDAP bind packet which will cause an overflow to occur this will cause the LDAP service to crash. The second uses a large malformed LDAP bind packet that is carefully crafted to take advantage of the buffer overflow and can be used to execute arbitrary code. Recommendations: Microsoft has made a patch available for the LDAP attack. Patch information is available at: http://www.microsoft.com/security/bulletins/ms99-009.asp Network administrators can protect internal systems from external attack by adding a rule to a filtering router or firewall of the type: Deny all incoming TCP packets with a destination port of 389. Many firewalls or packet filters may already have more restrictive rulesets that already encompass this filtering rule, in which case the network is already protected from an external attack. This ruleset would include filtering all incoming traffic to TCP port 389. Additional Information: These vulnerabilities were primarily researched by the ISS X-Force. ________ Copyright (c) 1999 by Internet Security Systems, Inc. Permission is hereby granted for the electronic redistribution of this Security Advisory. It is not to be edited in any way without express consent of the X-Force. If you wish to reprint the whole or any part of this Security Advisory in any other medium excluding electronic medium, please e-mail xforce@iss.net for permission. Internet Security Systems, Inc. (ISS) is the leading provider of adaptive network security monitoring, detection, and response software that protects the security and integrity of enterprise information systems. By dynamically detecting and responding to security vulnerabilities and threats inherent in open systems, ISS's SAFEsuite family of products provide protection across the enterprise, including the Internet, extranets, and internal networks, from attacks, misuse, and security policy violations. ISS has delivered its adaptive network security solutions to organizations worldwide, including firms in the Global 2000, nine of the ten largest U.S. commercial banks, and over 35 governmental agencies. For more information, call ISS at 678-443-6000 or 800-776-2362 or visit the ISS Web site at http://www.iss.net. 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X-Force Vulnerability and Threat Database: http://www.iss.net/xforce Please send suggestions, updates, and comments to: X-Force of Internet Security Systems, Inc. -----BEGIN PGP SIGNATURE----- Version: 2.6.3a Charset: noconv iQCVAwUBNu3GuzRfJiV99eG9AQF48wP+J1/vW040sA5f9Nz56JEF9s6d/tpainG1 Qw7Jxbry374IFinJZfk/K5FJkdbjJfMcyGfgWJjNriYZJ0EKFkQcRK7XNAUe8AGu LWaBW4l0v1Qox3ueR3GdCskQ8haK9vpxkFkbPmlefIWKMsVhncQPloJwU3/WyPNV uLJBWqHEpkU= =Zp+/ -----END PGP SIGNATURE----- ------------------------------------------------------------------------------ Date: Tue, 16 Mar 1999 22:28:11 -0800 From: aleph1@UNDERGROUND.ORG To: BUGTRAQ@netspace.org Subject: Microsoft Security Bulletin (MS99-009) The following is a Security Bulletin from the Microsoft Product Security Notification Service. Please do not reply to this message, as it was sent from an unattended mailbox. ******************************** Microsoft Security Bulletin (MS99-009) -------------------------------------- Patch Available for "Malformed Bind Request" Vulnerability Originally Posted: March 16, 1999 Summary ======= Microsoft has released a patch that eliminates a vulnerability in the LDAP Bind function for Microsoft (r) Exchange (r) 5.5. The vulnerability could allow denial of service attacks against an Exchange server or, under certain conditions, could allow arbitrary code to be run on the server. A fully supported patch is available, and Microsoft recommends that customers who are at risk from this attack download and install it. Issue ===== The Bind function in the Exchange 5.5 Directory Service has an unchecked buffer that poses two threats to safe operation. The first is a denial of service threat. A malformed Bind request could overflow the buffer, causing the Exchange Directory service to crash. The server would not need to be rebooted, but the Exchange Directory service, and possibly dependent services as well, would need to be restarted in order to resume messaging service. The second threat is more esoteric and would be far more difficult to exploit. A carefully-constructed Bind request could cause arbitrary code to execute on the server via a classic buffer overrun technique. Neither attack could occur accidentally. Customers who are using Exchange but who have turned off LDAP support in the Directory Service are not at risk from this vulnerability. Customers also can reduce their vulnerability to attacks from external sources by filtering incoming packets destined for TCP port 389, the LDAP service port. Microsoft has no reports of any customers being affected by this vulnerability. However, Microsoft is proactively releasing a patch that corrects the problem. Affected Software Versions ========================== - Microsoft Exchange Server 5.5 What Microsoft is Doing ======================= Microsoft has released patches that fix the problem identified. The patches are available for download from the sites listed below in What Customers Should Do. Microsoft also has sent this security bulletin to customers subscribing to the Microsoft Product Security Notification Service. See http://www.microsoft.com/security/services/bulletin.asp for more information about this free customer service. Microsoft has published the following Knowledge Base (KB) article on this issue: - Microsoft Knowledge Base (KB) article Q221989, XADM: Buffer Overrun in Exchange 5.5 LDAP Service, http://support.microsoft.com/support/kb/articles/q221/9/89.asp (Note: It might take 24 hours from the original posting of this bulletin for the KB article to be visible in the Web-based Knowledge Base.) What Customers Should Do ======================== Microsoft highly recommends that customers evaluate the degree of risk that this vulnerability poses to their systems and determine whether to download and install the patch. The patch can be found at: - X86-based Exchange: ftp://ftp.microsoft.com/bussys/exchange/exchange-public/ fixes/Eng/Exchg5.5/PostSP2/DIR-fix/PSP2DIRI.EXE - Alpha-based Exchange: ftp://ftp.microsoft.com/bussys/exchange/exchange-public/ fixes/Eng/Exchg5.5/PostSP2/DIR-fix/PSP2DIRA.EXE (Note: The above URLs have been wrapped for readability) More Information ================ Please see the following references for more information related to this issue. - Microsoft Security Bulletin MS99-009, Patch Available for "Malformed Bind Request" Vulnerability (the Web-posted version of this bulletin), http://www.microsoft.com/security/bulletins/ms99-009.asp. - Microsoft Knowledge Base (KB) article Q221989, XADM: Buffer Overrun in Exchange 5.5 LDAP Service. http://support.microsoft.com/support/kb/articles/q221/9/89.asp (Note: It might take 24 hours from the original posting of this bulletin for the KB article to be visible in the Web-based Knowledge Base.) Obtaining Support on this Issue =============================== If you require technical assistance with this issue, please contact Microsoft Technical Support. For information on contacting Microsoft Technical Support, please see http://support.microsoft.com/support/contact/default.asp. Revisions ========= - March 16, 1999: Bulletin Created For additional security-related information about Microsoft products, please visit http://www.microsoft.com/security ------------------------------------------------------------------------ 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. 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