[VulnWatch] iDEFENSE Security Advisory 03.21.05: Mac OS X CF_CHARSET_PATH Buffer Overflow Vulnerability

From: iDefense Customer Service (customerservice_at_idefense.com)
Date: 03/21/05

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    Date: Mon, 21 Mar 2005 17:00:05 -0500
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    Mac OS X CF_CHARSET_PATH Buffer Overflow Vulnerability

    iDEFENSE Security Advisory 03.21.05
    www.idefense.com/application/poi/display?id=219&type=vulnerabilities
    March 21, 2005

    I. BACKGROUND

    Mac OS X is an operating system for the Apple family of microcomputers.

    More information is available at the following link:
    http://www.apple.com/macosx/

    II. DESCRIPTION

    Local exploitation of a buffer overflow vulnerability within the Core
    Foundation Library included by default in Apple Computer Inc.'s Mac OS X

    could allow an attacker to gain root privileges.

    The vulnerability specifically exists due to improper handling of the
    CF_CHARSET_PATH environment variable. When a string greater than 1,024
    characters is passed via this variable, a stack-based overflow occurs,
    allowing the attacker to control program flow by overwriting the
    function's return address on the stack.

    Any application linked against the Core Foundation Library can be used
    as an exploit vector for this vulnerability. Some of the setuid root
    binaries that are vulnerable include su, pppd and login.

    III. ANALYSIS

    Successful exploitation of this vulnerability allows for root access. An

    attacker needs local access to the victim's system to exploit this
    vulnerability. This vulnerability is difficult to workaround due to the
    fact that a large number of system binaries are linked against the
    vulnerable code.

    IV. DETECTION

    iDEFENSE has confirmed this vulnerability in Mac OS X 10.3.5 and Mac OS
    X 10.3.6. Earlier versions are suspected vulnerable.

    V. WORKAROUND

    Restrict local access to trusted users only, as it is impossible to
    remove the setuid bit from the affected binaries without severely
    limiting the function of the system.

    VI. VENDOR RESPONSE

    This vulnerability is addressed in Apple Security Update 2005-003
    available at:

       http://docs.info.apple.com/article.html?artnum=301061

    VII. CVE INFORMATION

    The Common Vulnerabilities and Exposures (CVE) project has assigned the
    name CAN-2005-0716 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

    02/04/2005 Initial vendor notification
    02/04/2005 Initial vendor response
    03/21/2005 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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