iDEFENSE Security Advisory 04.06.05: IBM Lotus Domino Server Web Service DoS Vulnerability

From: iDEFENSE Labs (labs-no-reply_at_idefense.com)
Date: 04/06/05

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To: <bugtraq@securityfocus.com>, <vulnwatch@vulnwatch.org>

    IBM Lotus Domino Server Web Service DoS Vulnerability

    iDEFENSE Security Advisory 04.06.05
    http://www.idefense.com/application/poi/display?type=vulnerabilities
    April 6, 2005

    I. BACKGROUND

    IBM Lotus Domino Server software provides messaging, calendaring and
    scheduling capabilities on a variety of operating systems. More
    information about the product is available from:

        http://www.lotus.com/products/product4.nsf/wdocs/dominohomepage

    II. DESCRIPTION

    Remote exploitation of a denial of service vulnerability in IBM Corp.'s
    Lotus Domino Server web service allows attackers to crash the service,
    thereby preventing legitimate access.

    The problem specifically exists within the module NLSCCSTR.DLL. A
    recursive call loop is made continually when parsing the following
    example GET request:

        GET /cgi-bin/[xxx] HTTP/1.0
        Host: 10.10.0.100

    Where [xxx] represents a long string (~330) of UNICODE decimal value 430
    characters. The request triggers a stack exhaustion, which during
    testing against Lotus Domino Server version 6.5.1 occurred at the
    following instruction just prior to a call to NLSCCSTR.ucnv_toUnicode():

        6236B82B PUSH ECX

    This results in the immediate crash of nHTTP.EXE and is not reported to
    the NSERVER terminal. The crash occurs only when the long string is
    prefixed with /cgi-bin/, as Lotus Domino Server uses two different
    routines when handling requests made to the root directory and cgi-bin.
    Examining the call stack at the time of crash reveals the issue. The
    procedure NLSCCSTR.6236B080 is recursively called from the instruction
    at address NLSCCSTR.6236B73D. A condition that is checked earlier would
    JMP over this recursive call:

        PROCEDURE NLSCCSTR.6236B080 (Lotus Domino Server 6.5.1)
                ...
                6236B70D TEST EAX, EAX
            +-< 6236B70F JE SHORT NLSCCSTR.6236B77D
            | ...
            | 6236B73D CALL NLSCCSTR.6236B080
            | ...
            +-> 6236B77D MOV EAX, [EBP+20]

    Further up the call stack we can find the following originating calls
    with symbolic names:

        Procedure=NLSCCSTR.ccSTRCpyXlateExt
        Called from=NLSCCSTR.623DF3B8
        
        Procedure=nnotes.NLS_xlate_string32
        Called from=nnotes.60197A09

    While portions of the stack are overwritten with attacker-supplied data,
    gaining flow control to execute arbitrary code does not seem possible.

    III. ANALYSIS

    Exploitation of this vulnerability allows unauthenticated remote
    attackers to crash the web service, thereby preventing legitimate usage.
    This attack requires minimal resources to launch and can be repeated to
    ensure that an unpatched computer is unable to recover. A successful
    attack does not generate error messages in the NSERVER terminal.
    However, the nHTTP.exe process has indeed crashed.

    Restarting Domino Server will resume normal functionality.

    IV. DETECTION
     iDEFENSE has confirmed the existence of this vulnerability in Lotus
    Domino Server version 6.5.1. It has been reported that Lotus Domino
    Server 6.03 is also vulnerable. It is suspected that earlier versions of
    Lotus Domino Server are also affected. Additionally, iDEFENSE has
    confirmed that Lotus Domino Server version 6.5.3 is not affected by this
    issue.

    V. WORKAROUND

    Employ firewalls, access control lists or other TCP/UDP restriction
    mechanisms to limit access to systems and services.

    VI. VENDOR RESPONSE

    IBM has released technote #1202446 for this issue. The vendor has been
    unable to reproduce the issue and has therefore not released any
    patches. iDEFENSE Labs testing has shown this product to be vulnerable
    to the issue described in this report. Customers should consider
    upgrading to Lotus Domino Server version 6.5.3, which iDEFENSE has
    confirmed as being not vulnerable.

    VII. CVE INFORMATION

    A Mitre Corp. Common Vulnerabilities and Exposures (CVE) number has not
    been assigned yet.

    VIII. DISCLOSURE TIMELINE

    02/07/2005 Initial vendor notification
    02/09/2005 Initial vendor response
    04/06/2005 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@idefense.com 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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