-----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 xforceat_private 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. Disclaimer The information within this paper may change without notice. Use of this information constitutes acceptance for use in an AS IS condition. There are NO warranties with regard to this information. In no event shall the author be liable for any damages whatsoever arising out of or in connection with the use or spread of this information. Any use of this information is at the user's own risk. X-Force PGP Key available at: http://www.iss.net/xforce/sensitive.html as well as on MIT's PGP key server and PGP.com's key server. X-Force Vulnerability and Threat Database: http://www.iss.net/xforce Please send suggestions, updates, and comments to: X-Force <xforceat_private> 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-----
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