[VulnWatch] iDEFENSE Security Advisory 10.20.05: Multiple Vendor Ethereal srvloc Buffer Overflow Vulnerability

From: iDEFENSE Labs (labs-no-reply_at_idefense.com)
Date: 10/20/05

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    Date: Thu, 20 Oct 2005 17:35:06 -0400
To: <bugtraq@securityfocus.com>, <vulnwatch@vulnwatch.org>, <full-disclosure@lists.grok.org.uk>

    Multiple Vendor Ethereal srvloc Buffer Overflow Vulnerability

    iDEFENSE Security Advisory 10.20.05
    www.idefense.com/application/poi/display?id=323&type=vulnerabilities
    October 20, 2005

    I. BACKGROUND

    Ethereal is a full featured open source network protocol analyzer. For
    more information, see http://www.ethereal.com/

    II. DESCRIPTION

    Remote exploitation of a buffer overflow vulnerability in the Service
    Location Protocol (srvloc) dissectors within Ethereal, as included in
    various vendors' operating system distributions, could allow attackers
    to crash the vulnerable process or execute arbitrary code.

    The vulnerable code follows:

    ./epan/dissectors/packet-srvloc.c:429

    static guint8*
    unicode_to_bytes(tvbuff_t *tvb, int offset, int length, gboolean
    endianness)
    {
      const char *ascii_text = tvb_get_ptr(tvb, offset, length);
      int i, j=0;
      guint8 c_char, c_char1;
      static guint8 byte_array[255];

      if (endianness) {
        ...
          }
      }
      else
      {
          for (i = 0; i < length; i++) {
            c_char = ascii_text[i];
            if (c_char != 0) {
                byte_array[j] = c_char;
                j++;
            }
          }
      }

      byte_array[j]=0;
      return byte_array;
    }

    This function is called with a user-controlled length value on line 581
    in the same file. This allows an attacker to cause an overflow of the
    byte_array array, as values greater than 255 may be specified. In lab
    analysis, it has been demonstrated that there are several interesting
    values beyond this array that make arbitrary code execution possible.

    To cause Ethereal to dissect an arbitrary packet with the srvloc
    dissector, the source or destination port must be set to TCP port 427,
    and the destination port must not be a port with any registered
    dissector. As Ethereal does not keep state, a single spoofed TCP data
    packet can be used to exploit this vulnerability, regardless of whether
    there are any ports listening on either end.

    III. ANALYSIS

    Exploitation could result in remote root access, as Ethereal must have
    root privileges to open a raw socket.

    Ethereal is often used by network administrators to debug network
    problems and compromise of a network administrators machine can lead to
    further compromise of the network.

    IV. DETECTION

    Ethereal versions 0.10.12 and earlier are reportedly vulnerable. The
    following vendors include susceptible Ethereal packages within their
    respective operating system distributions:

            The Debian Project: Debian GNU/Linux 3.0
            The FreeBSD Project: FreeBSD 5.4 and earlier
            Gentoo Foundation Inc.: Gentoo Linux 2004.0, 2004.1, 2004.2,
    2004.3
              and 2005.0
            Mandriva SA: Mandriva Linux 10.1, 10.1 (x86_64),
              LE2005 and LE2005 (x86_64)
            Novell Inc.: SUSE Linux versions 9.0, 9.1, 9.2 and 9.3
            Red Hat Inc.: Fedora Core 3 and 4
        Red Hat Desktop (v. 3) Red Hat Desktop (v. 4)
        Red Hat Enterprise Linux AS (v. 2.1)
        Red Hat Enterprise Linux AS (v. 3)
        Red Hat Enterprise Linux AS (v. 4)
        Red Hat Enterprise Linux ES (v. 2.1)
        Red Hat Enterprise Linux ES (v. 3)
        Red Hat Enterprise Linux ES (v. 4)
        Red Hat Enterprise Linux WS (v. 2.1)
        Red Hat Enterprise Linux WS (v. 3)
        Red Hat Enterprise Linux WS (v. 4)
        Red Hat Linux Advanced Workstation 2.1 for the Itanium Processor

    V. WORKAROUND

    When using Ethereal, use the following filter to disable port 427, and
    therefore, automatic srvloc dissection:

            not port 427

    VI. VENDOR RESPONSE

    The vendor has addressed this issue in ethereal 0.10.13, available for
    download at:

       http://www.ethereal.com/download.html

    VII. CVE INFORMATION

    The Common Vulnerabilities and Exposures (CVE) project has assigned the
    name CAN-2005-3184 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
    10/20/2005 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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