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iDEFENSE Security Advisory 10.20.05: Multiple Vendor Ethereal srvloc Buffer Overflow Vulnerability
From: "iDEFENSE Labs" <labs-no-reply () idefense com>
Date: Thu, 20 Oct 2005 17:35:06 -0400

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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