[VulnWatch] iDEFENSE Security Advisory 10.13.05: Multiple Vendor wget/curl NTLM Username Buffer Overflow Vulnerability

From: iDEFENSE Labs (labs-no-reply_at_idefense.com)
Date: 10/13/05

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To: <bugtraq@securityfocus.com>, <vulnwatch@vulnwatch.org>, <full-disclosure@lists.grok.org.uk>

    Multiple Vendor wget/curl NTLM Username Buffer Overflow Vulnerability

    iDEFENSE Security Advisory 10.13.05
    www.idefense.com/application/poi/display?id=322&type=vulnerabilities
    October 13, 2005

    I. BACKGROUND

    GNU Wget is a free software package for retrieving files using HTTP,
    HTTPS and FTP, the most widely-used Internet protocols. It is a
    non-interactive commandline tool, so it may easily be called from
    scripts, cron jobs, terminals without X-Windows support, etc. More
    information on Wget is available from the vendor website:

            http://www.gnu.org/software/wget/wget.html

    curl is a command line tool for transferring files with URL syntax,
    supporting FTP, FTPS, HTTP, HTTPS, GOPHER, TELNET, DICT, FILE and LDAP.
    Curl supports HTTPS certificates, HTTP POST, HTTP PUT, FTP uploading,
    HTTP form based upload, proxies, cookies, user+password authentication
    (Basic, Digest, NTLM, Negotiate, kerberos...), file transfer resume,
    proxy tunneling and a busload of other useful tricks. More information
    on curl is available from the vendor website:

            http://curl.haxx.se/

    II. DESCRIPTION

    Remote exploitation of a buffer overflow vulnerability in multiple
    vendor's implementations of curl and wget allows attackers to execute
    arbitrary code.

    The vulnerability specifically exists due to insufficient bounds
    checking on user-supplied data supplied to a memory copy operation. The
    memcpy() of the supplied ntlm username to ntlmbuf shown below results
    in a stack overflow:

    http-ntlm.c in ntlm_output() on line 532:

        /* size is now 64 */
        size=64;
        ntlmbuf[62]=ntlmbuf[63]=0;

        memcpy(&amp;ntlmbuf[size], domain, domlen);
        size += domlen;

        memcpy(&amp;ntlmbuf[size], usr, userlen);
        size += userlen;

    The resulting stack overflow can be leveraged to gain arbitrary code
    execution with user privileges.

    III. ANALYSIS

    Successful exploitation of the vulnerability allows remote attackers to
    execute arbitrary code with permissions of the http client process.
    User interaction is required. Exploitation requires a user to use one
    of the affected clients to connect to a malicious website.

    This vulnerability affects both wget and curl clients similarly because
    wget 1.10 adopted the curl ntlm authentication source code into its own
    code base. The described vulnerability requires that ntlm authentication

    is enabled in the affected client versions. A factor that somewhat
    increases the risk of this vulnerability is that a client can be forced
    to reconnect using ntlm authentication by issuing a HTTP 302 REDIRECT
    command to the connecting client.

    IV. DETECTION

    iDEFENSE Labs has confirmed the following software versions are
    vulnerable:

        * wget 1.10
        * curl 7.13.2
        * libcurl 7.13.2

    V. WORKAROUND

    As a workaround solution, disable NTLM support in wget and curl
    installations.

    VI. VENDOR RESPONSE

    wget 1.10.2 has been released to address this issue and is available for
    download at:

       http://ftp.gnu.org/pub/gnu/wget/

    curl has released the following patch to address this issue:

       http://curl.haxx.se/libcurl-ntlmbuf.patch

    curl has also released the following security advisory:

       http://curl.haxx.se/mail/lib-2005-10/0061.html
       
    Additionally, the maintainers of curl-web have provided the following
    details on affected versions:

    Affected versions: curl and libcurl 7.10.6 to and including 7.14.1

    Not affected versions: curl and libcurl 7.10.5 and earlier,
      7.15.0 and later

    VII. CVE INFORMATION

    The Common Vulnerabilities and Exposures (CVE) project has assigned the
    name CAN-2005-3185 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

    10/12/2005 Initial vendor notification
    10/12/2005 Initial vendor response
    10/13/2005 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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