[Full-disclosure] iDEFENSE Security Advisory 04.26.05: Citrix Program Neighborhood Agent Buffer Overflow

From: iDEFENSE Labs (labs-no-reply_at_idefense.com)
Date: 04/26/05

  • Next message: Martin Schulze: "[Full-disclosure] [SECURITY] [DSA 714-1] New kdelibs packages fix arbitrary code execution"
    Date: Tue, 26 Apr 2005 11:12:44 -0400
    To: <bugtraq@securityfocus.com>, <vulnwatch@vulnwatch.org>, <full-disclosure@lists.grok.org.uk>

    Citrix Program Neighborhood Agent Buffer Overflow

    iDEFENSE Security Advisory 04.26.05
    April 26, 2005


    Citrix Program Neighborhood Agent is a part of the Citrix Presentation
    Server Client and facilitates access to Citrix published applications.


    Remote exploitation of a buffer overflow vulnerability in Citrix Systems
    Inc.'s Program Neighborhood Agent allows attackers to execute arbitrary
    code under the privileges of the client user.

    The problem specifically exists in the client code responsible for
    handling the caching of information received from the server. The
    Program Neighborhood Agent caches information from published
    applications in the AppCache folder, located in the users profile
    directory. Cached icon filenames are named after the published
    application. The filename is constructed from a series of calls to
    lstrcatA() into a stack based buffer. Because of insufficient bounds
    checking, a stack based buffer overflow can occur after the second call
    to lstrcatA() as the filename read from the XML element <InName> is
    being added to the AppCache folder path. This leads to the eventual
    execution of arbitrary code.


    Successful exploitation allows remote attackers to execute arbitrary
    code under the privileges of the client user. Exploitation requires that
    an attacker establish a malicious server and cause or convince the
    target user to connect to it via the Program Neighborhood Agent. This
    can be accomplished by social engineering or automatically when combined
    with a DNS or ARP spoofing attack.

    Exploitation of this vulnerability is not trivial. In order to exploit
    this vulnerability reliably, an attacker must determine the length of
    the target user's username. In some cases, this information can be
    gleaned with standard Windows tools such as NBTSTAT. Furthermore,
    because requests are cached by the client, an attacker in most cases has
    only one window of opportunity to perform a successful attack.


    iDEFENSE has confirmed the existance of this vulnerability in Citrix
    MetaFrame Program Neighborhood v8.00.24737. It is suspected that earlier
    versions are also vulnerable.


    Utilize the server IP address instead of the name to circumvent DNS
    spoofing attacks.


    A vendor advisory for this vulnerability is available at:

    Updated clients to address this vulnerability are available at:


    The Common Vulnerabilities and Exposures (CVE) project has assigned the
    names CAN-2004-1078 to these issues. This is a candidate for inclusion
    in the CVE list (http://cve.mitre.org), which standardizes names for
    security problems.


    11/23/2004 Initial vendor notification
    11/24/2004 Initial vendor response
    04/26/2005 Coordinated public disclosure


    Patrik Karlsson (cqure.net) is credited with this discovery.

    Get paid for vulnerability research

    Free tools, research and upcoming events


    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.
    Full-Disclosure - We believe in it.
    Charter: http://lists.grok.org.uk/full-disclosure-charter.html
    Hosted and sponsored by Secunia - http://secunia.com/

  • Next message: Martin Schulze: "[Full-disclosure] [SECURITY] [DSA 714-1] New kdelibs packages fix arbitrary code execution"