AUSCERT External Security Bulletin Redistribution
         ESB-2000.026 -- REVISED HP SECURITY BULLETIN HPSBUX0001-110
                      Vulnerability with PMTU strategy
                               15 February 2000


Hewlett-Packard has released the following revised bulletin concerning a
vulnerability in HP-UX release 10.30, 11.00 and 11.04 only.
This vulnerability may be exploited to cause the affected system to flood
another system with IP packets which may result in a denial of service.

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Document ID:  HPSBUX0001-110
Date Loaded:  20000213
      Title:  Security Vulnerability with PMTU strategy (revised)

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Last Revised:  11 Feb. 2000
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The information in the following Security Advisory should be acted upon
as soon as possible.  Hewlett-Packard Company will not be liable for any
consequences to any customer resulting from customer's failure to fully
implement instructions in this Security Advisory as soon as possible.

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PROBLEM:  An HP-UX 10.30, 11.00, or 11.04 system can be used as an IP
          traffic amplifier.  Small amounts of inbound traffic can result
          in larger amounts of outbound traffic.

- ---->>>   HP-UX releases 10.30, 11.00 and 11.04 only.

DAMAGE:   Depending upon the amount and nature of inbound traffic, an
          HP-UX 10.30/11.00/11.04 system can be used to flood a target
          system with IP packets which could result in a denial of

SOLUTION: Set the NDD parameter ip_pmtu_strategy to 1.

AVAILABILITY: This capability is already available.
CHANGE SUMMARY:  Added HP-UX VirtualVault release 11.04.
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   A. Background
      HP provides a proprietary method for determining PMTU.  When
      traffic needs to be routed to a destination for which the optimum
      MTU has not been determined, ICMP packets are used to discover
      the MTU for that path while data traffic is shipped in parallel.
      This is the default strategy for determining PMTU.

   B. Recommended solution
      Reference ndd manpage (1M), /etc/rc.config.d/nddconf

      To ensure that this parameter is set each time the system
      is booted, add the following lines to /etc/rc.config.d/nddconf


      The value of <index> is an integer from 0 to 99.  The first
      parameter specified in the file should use an <index> of
      0, the second an <index> of 1, and so on.

      Once these changes have been made, execute the following

      /usr/bin/ndd -c

      This sets all of the options specified in the file

      To verify that the parameter is set correctly, use the following
                /usr/bin/ndd -get /dev/ip ip_pmtu_strategy

      This should report a value of 1.

      Another way to  change the ip_pmtu_strategy parameter on a running
      system is to use the following NDD command:

                /usr/bin/ndd -set /dev/ip ip_pmtu_strategy 1

      This setting will only last until the system is rebooted
      at which point the value of the parameter will be determined by the
      default value of 2 or whatever value is set in

   C. To subscribe to automatically receive future NEW HP Security
      Bulletins from the HP IT Resource Center via electronic mail,
      do the following:

      Use your browser to get to the HP IT Resource Center page

               (for US, Canada, Asia-Pacific, & Latin-America)
        http://europe-support.external.hp.com     (for Europe)

      Under the Maintenance and Support Menu (Electronic Support Center):
        click on the "more..." link.  Then -

      To -subscribe- to future HP Security Bulletins, or
      To -review- bulletins already released
        click on "Support Information Digests" near the bottom of the
        page, under "Notifications".

      Login with your user ID and password (or register for one).
      (Remember to save the User ID assigned to you, and your password).

      On the "Support Information Digest Main" page:
      click on the "HP Security Bulletin Archive".

      Once in the archive the third link is to our current Security
      Patch Matrix.  Updated daily, this matrix categorizes security
      patches by platform/OS release, and by bulletin topic.

      The security patch matrix is also available via anonymous ftp:


    E. To report new security vulnerabilities, send email to

       Please encrypt any exploit information using the security-alert
       PGP key, available from your local key server, or by sending a
       message with a -subject- (not body) of 'get key' (no quotes) to

      Permission is granted for copying and circulating this Advisory to
      Hewlett-Packard (HP) customers (or the Internet community) for the
      purpose of alerting them to problems, if and only if, the Advisory
      is not edited or changed in any way, is attributed to HP, and
      provided such reproduction and/or distribution is performed for
      non-commercial purposes.

      Any other use of this information is prohibited.  HP is not liable
      for any misuse of this information by any third party.
- -----End of Document ID:  HPSBUX0001-110--------------------------------------

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