Original issue date: December 18, 1996<BR>
Last revised: December 5, 1997<BR>
 Updated information for NCR Corporation.

<P>A complete revision history is at the end of this file.

<P>The CERT Coordination Center has received reports of a
denial-of-service attack using large ICMP datagrams. Exploitation
details involving this vulnerability have been widely distributed.

<P>The CERT/CC team recommends installing vendor patches as they
become available.

<P>We will update this advisory as we receive additional
information. Please check advisory files regularly for updates that
relate to your site.

<H2>I. Description</H2>

<P>The TCP/IP specification (the basis for many protocols used on the
Internet) allows for a maximum packet size of up to 65536 octets (1
octet = 8 bits of data), containing a minimum of 20 octets of IP
header information and 0 or more octets of optional information, with
the rest of the packet being data. It is known that some systems will
react in an unpredictable fashion when receiving oversized IP
packets. Reports indicate a range of reactions including crashing,
freezing, and rebooting.

<P>In particular, the reports received by the CERT Coordination Center
indicate that Internet Control Message Protocol (ICMP) packets issued
via the &quot;ping&quot; command have been used to trigger this
behavior. ICMP is a subset of the TCP/IP suite of protocols that
transmits error and control messages between systems. Two specific
instances of the ICMP are the ICMP ECHO_REQUEST and ICMP ECHO_RESPONSE
datagrams. These two instances can be used by a local host to
determine whether a remote system is reachable via the network; this
is commonly achieved using the &quot;ping&quot; command.

<P>Discussion in public forums has centered around the use of the
&quot;ping&quot; command to construct oversized ICMP datagrams (which
are encapsulated within an IP packet). Many ping implementations by
default send ICMP datagrams consisting only of the 8 octets of ICMP
header information but allow the user to specify a larger packet size
if desired.

<P>You can read more information about this vulnerability on Mike
Bremford's Web page. (Note that this is not a CERT/CC maintained
page. We provide the URL here for your convenience.)

<A HREF=http://www.sophist.demon.co.uk/ping/index.html>

<H2>II. Impact</H2>

<P>Systems receiving oversized ICMP datagrams may crash, freeze, or
reboot, resulting in denial of service.

<H2>III. Solution</H2>

<P>First, since crashing a router or firewall may be part of a larger,
multistage attack scenario, we encourage you to inspect the running
configuration of any such systems that have crashed to ensure that the
configuration information is what you expect it to be.

<P>Then install a patch from your vendor.

<P>Below is a list of vendors who have provided information about
patches for this problem. Details are in Appendix A of this advisory;
we will update the appendix as we receive more information. If your
vendor's name is not on this list, please contact the vendor directly.

           Berkeley Software Design, Inc. (BSDI)<BR>
           Computer Associates, Intl. (products for NCR)<BR>
           Cray Research<BR>
           Digital Equipment Corporation<BR>
           Free BSD, Inc.<BR>
           Hewlett-Packard Company<BR>
           IBM Corporation<BR>
           Linux Systems<BR>
           NCR Corporation<BR>
           NEC Corporation<BR>
           Open Software Foundation (OSF)<BR>
           The Santa Cruz Operation, Inc. (SCO)<BR>
Sun Microsystems, Inc.

<H2>Appendix A - Vendor Information</H2>

<P>Below is a list of the vendors who have provided information for
this advisory. We will update this appendix as we receive additional
information.  If you do not see your vendor's name, please contact the
vendor directly.

<H3>Berkeley Software Design, Inc. (BSDI)</H3>

BSD/OS 2.1 is not vulnerable to this problem.  It correctly handles
large packets without any problems.
<H3>Computer Associates, Intl.</H3>

(products for NCR)

<P>Not vulnerable.

<H3>Cray Research</H3>

Attempts to send oversized ICMP datagrams are rejected with
appropriate error messages.  We believe that oversized ICMP datagrams
sent to Unicos systems will also be rejected without crashing.

<H3>Data General Corporation</H3>

Due to the way DG/UX processes tcp packets, DG/UX is not vulnerable to
this attack.

<H3>Digital Equipment Corporation</H3>

MSG ID: SSRT0429 From DSNlink/DIA Database

<P>The following is important information concerning a potential denial of
service issue which affects Digital UNIX Operating System, Digital UNIX
MLS+, Firewall implementations, and Digital TCP/IP Services for OpenVMS AXP &amp;

COMPONENT:  System Security / Potential Denial of Service

  DIGITAL UNIX     Version: 3.0, 3.0b, 3.2, 3.2c, 3.2de1, 3.2de2,
                            3.2f, 3.2g, 4.0, 4.0a
  DIGITAL UNIX MLS+ Version 3.1a
  DIGITAL TCP/IP Services for OpenVMS AXP & VAX Versions - 4.0, 4.1
  DIGITAL ULTRIX Versions 4.3, 4.3a, 4.4, 4.5
  DIGITAL Firewall for UNIX
  DIGITAL AltaVista Firewall for UNIX
For more information check the DSNlink/DIA Articles (keyword PING), or the
URL http://www.service.digital.com/html/whats-new.html for the latest


<P>Digital recently discovered a potential denial of service issue that
may occur by remote systems exploiting a recently published problem while
executing the 'ping' command. Solutions and initial communications
began appearing in DSNlink/DIA FLASH/articles in late October, 1996.



<P>Digital has reacted promptly to this reported problem and a complete
set of patch kits are being prepared for all currently supported

<P>The Digital patches may be obtained from your local Digital support
channel or from the URL listed above. Please refer to the applicable README
notes information prior to the installation of patch kits on your system.

<P>Copyright (c) Digital Equipment Corporation, 1996, All Rights Reserved.
Unpublished Rights Reserved Under The  Copyright Laws Of The United States.

<H3>Free BSD, Inc.</H3>

We have fixed the problem in 2.1.6 and -current.

<H3>Hewlett-Packard Company</H3>

For HP9000 Series 700 and 800 systems, apply the appropriate patch.
See Hewlett-Packard Security Bulletin #000040 (HPSBUX9610-040) for further
details. The bulletin is available from the HP SupportLine and
<A HREF=ftp://ftp.cert.org/pub/vendors/hp/>ftp://ftp.cert.org/pub/vendors/hp/</A>

          Patch Name(Platform/OS)   | Notes
          PHNE_9027 (s700 9.01)     : PHNE_7704 must first be installed
          PHNE_9028 (s700 9.03/5/7) : PHNE_7252 must first be installed
          PHNE_9030 (s700 10.00)    :             No patch dependencies
          PHNE_9032 (s700 10.01)    : PHNE_8168 must first be installed
          PHNE_9034 (s700 10.10)    : PHNE_8063 must first be installed
          PHNE_9036 (s700 10.20)    :             No patch dependencies
          PHNE_8672 (s800 9.00)     : PHNE_7197 must first be installed
          PHNE_9029 (s800 9.04)     : PHNE_7317 must first be installed
          PHNE_9031 (s800 10.00)    :             No patch dependencies
          PHNE_9033 (s800 10.01)    : PHNE_8169 must first be installed
          PHNE_9035 (s800 10.10)    : PHNE_8064 must first be installed
          PHNE_9037 (s800 10.20)    :             No patch dependencies
For our MPE operating system, patches are in process. Watch for the issuance
of our MPE security bulletin.

<H3>IBM Corporation</H3>

See the appropriate release below to determine your action.

<H4>AIX 3.2</H4>

Apply the following fix to your system:

<P>APAR - IX59644 (PTF - U444227 U444232)

<P>To determine if you have this PTF on your system, run the following
          lslpp -lB U444227 U444232

<H4>AIX 4.1</H4>
Apply the following fix to your system:

<P>APAR - IX59453

<P>To determine if you have this APAR on your system, run the following
          instfix -ik IX59453
Or run the following command:
          lslpp -h bos.net.tcp.client
Your version of bos.net.tcp.client should be or later.

<H4>AIX 4.2</H4>

Apply the following fix to your system:

<P>APAR - IX61858

<P>To determine if you have this APAR on your system, run the following
          instfix -ik IX61858
Or run the following command:
          lslpp -h bos.net.tcp.client
Your version of bos.net.tcp.client should be or later.
<H4>IBM SNG Firewall</H4>

NOTE: The fixes in this section should ONLY be applied to systems
running the IBM Internet Connection Secured Network Gateway (SNG)
firewall software.  They should be applied IN ADDITION TO the IBM
AIX fixes listed in the previous section.

<H4>IBM SNG V2.1</H4>

APAR - IR33376 PTF UR46673

<H4>IBM SNG V2.2</H4>

APAR - IR33484 PTF UR46641

<H4>To Order</H4>

APARs may be ordered using Electronic Fix Distribution (via FixDist)
or from the IBM Support Center.  For more information on FixDist,
reference URL:

<A HREF=http://service.software.ibm.com/aixsupport/>http://service.software.ibm.com/aixsupport/</A>

<P>or send e-mail to 
	<A HREF=mailto:aixserv@austin.ibm.com>aixserv@austin.ibm.com</A> 
with a subject of &quot;FixDist&quot;.

<P>IBM and AIX are registered trademarks of International Business Machines

<H3>Linux Systems</H3>

We recommend that you upgrade your Linux 1.3.x and 2.0.x kernels to Linux
2.0.27. This is available from all the main archive sites such as

<A HREF=ftp://ftp.cs.helsinki.fi/pub/Software/Linux>ftp://ftp.cs.helsinki.fi/pub/Software/Linux</A>

<P>Users wishing to remain with an earlier kernel version may download a
patch from <A HREF=http://www.uk.linux.org/big-ping-patch>http://www.uk.linux.org/big-ping-patch</A>. 
This patch will work with
2.0.x kernel revisions but is untested with 1.3.x kernel revisions.

<P>Red Hat Linux has chosen to issue a 2.0.18 based release with the fix. Red
Hat users should obtain this from

<A HREF=ftp://ftp.redhat.com/pub/redhat/redhat-4.0/updates/i386/kernel-2.0.18-6.i386.rpm>ftp://ftp.redhat.com/pub/redhat/redhat-4.0/updates/i386/kernel-2.0.18-6.i386.rpm</A>

<H3>NCR Corporation</H3>
For MP-RAS 3.00 and above, using TCP/IP as package name "inet",
not vulnerable.

<H3>NEC Corporation</H3>

- --------------------------------------------------------------------------
       OS               Version        Status
- ------------------   ------------   -------------------------------------
EWS-UX/V(Rel4.0)     R1.x - R6.x    not vulnerable
EWS-UX/V(Rel4.2)     R7.x - R10.x   not vulnerable
EWS-UX/V(Rel4.2MP)   R10.x          not vulnerable
UP-UX/V              R1.x - R4.x    not vulnerable
UP-UX/V(Rel4.2MP)    R5.x - R7.x    not vulnerable
UX/4800              R11.x          not vulnerable
- --------------------------------------------------------------------------



see Computer Associates, Intl.
<H3>Open Software Foundation (OSF)</H3>

OSF's OSF/1 R1.3.3 maintenance release includes a solution for this

<H3>The Santa Cruz Operation, Inc. (SCO)</H3>

The following SCO products are known to be vulnerable:
  SCO OpenServer 5.0.0, 5.0.2<BR>
  SCO Internet FastStart 1.0.0, 1.1.0<BR>
  SCO Open Desktop 3.0<BR>
SCO TCP/IP 1.2.1 on SCO Unix System V/386 Release 3.2 Version 4.2
The symptoms encountered vary greatly and seem to be related to the type
of network interface device being used. Support Level Supplement (SLS)
OSS449 addresses this problem for the following releases:
  SCO OpenServer 5.0.0, 5.0.2<BR>
SCO Internet FastStart 1.0.0, 1.1.0.
This Supplement is available at the following URLs:

<P><A HREF="ftp://ftp.sco.COM/SLS/oss449a.ltr">ftp://ftp.sco.COM/SLS/oss449a.ltr</A>  (cover letter)<BR>
<A HREF="ftp://ftp.sco.COM/SLS/oss449a.Z">
ftp://ftp.sco.COM/SLS/oss449a.Z</A>    (image)

<P>The checksums are as follows:
 sum -r
        oss449a.ltr:    28877   42
          oss449a.Z:    54558 1762

        MD5 (oss449a.Z) = e8fc8a29dd59683ce5107f3b9b8d1169
        MD5 (oss449a.ltr) = d51ee1caf33edb86f4dbeb1733c99d86

<P>If this SLS is ever updated, it will be noted at:

<A HREF="ftp://ftp.sco.COM/SLS/README">ftp://ftp.sco.COM/SLS/README</A>

<P>Should more information become available for either SCO's OpenServer or
UnixWare products, SCO will provide updated information for this advisory.

<P>If you need further assistance, SCO's Web page is at <A HREF="http://www.sco.COM">http://www.sco.COM</A>.

<P>Support requests from supported customers may be addressed to
<A HREF="mailto:support@sco.COM">support@sco.COM</A> 
, or you may contact SCO as follows:

<P>USA/Canada: 6am-5pm Pacific Standard Time (PST)
        1-408-425-4726  (voice)<BR>
1-408-427-5443  (fax)

<P>Pacific Rim, Asia, and Latin American customers: 6am-5pm Pacific
Standard Time (PST)<BR>

        1-408-425-4726  (voice)<BR>
1-408-427-5443  (fax)

<P>Europe, Middle East, Africa: 9am-5:00pm Greenwich Mean Time (GMT)
        +44 1923 816344 (voice)<BR>
+44 1923 817781 (fax)

<H3>Sun Microsystems, Inc.</H3>
Sun Microsystems has provided the following list of patches in response
to this advisory: 
        103630-09 5.5.1
        103631-09 5.5.1_x86
        103169-12 5.5
        103170-12 5.5_x86
        101945-51 5.4
        101946-45 5.4_x86

<P>The CERT Coordination Center staff thanks AUSCERT, the Australian
Computer Emergency Response Team, and DFN-CERT, the German team, for
their contributions to this advisory, and we thank Mike Bremford for
permission to cite the information he has made available to the


<!--#include virtual="/include/footer_nocopyright.html" -->
<P>Copyright 1996 Carnegie Mellon University.</P>


Revision History
Dec. 5, 1997  Appendix A - Updated information for NCR Corporation.
Sep. 24,1997  Updated copyright statement
Aug. 7, 1997  Changed vendor information for Sun Microsystems to remove
              incorrect patch reference.
July 28, 1997 Added vendor information for Sun Microsystems.
Jan. 20, 1997 Appendix A - added information from Data General Corporation.
Jan. 14, 1997 Appendix A - modified SCO entry to include updated patch