AUSCERT External Security Bulletin Redistribution

                 ESB-2001.276 -- CERT Advisory CA-2001-17
                   Check Point RDP Bypass Vulnerability
                               10 July 2001


        AusCERT Security Bulletin Summary

Product:                Check Point VPN-1
                        FireWall-1 Version 4.1
Vendor:                 Check Point
Impact:                 Inappropriate Access
Access Required:        Remote

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CERT Advisory CA-2001-17 Check Point RDP Bypass Vulnerability

   Original release date: July 09, 2001
   Last revised: --
   Source: CERT/CC

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

Systems Affected

     * Check Point VPN-1 and FireWall-1 Version 4.1


   A vulnerability in Check Point FireWall-1 and VPN-1 may allow an
   intruder to pass traffic through the firewall on port 259/UDP.

I. Description

   Inside Security GmbH has discovered a vulnerability in Check Point
   FireWall-1 and VPN-1 that allows an intruder to bypass the firewall.
   The default FireWall-1 management rules allow arbitrary RDP (Reliable
   Data Protocol) connections to traverse the firewall. RFC-908 and
   RFC-1151 describe the Reliable Data Protocol (RDP). Quoting from

     The Reliable Data Protocol (RDP) is designed to provide a reliable
     data transport service for packet-based applications such as remote
     loading and debugging.

   RDP was designed to have much of the same functionality as TCP, but it
   has some advantages over TCP in certain situations. FireWall-1 and
   VPN-1 include support for RDP, but they do not provide adequate
   security controls. Quoting from the advisory provided by Inside
   Security GmbH:

     By adding a faked RDP header to normal UDP traffic any content can
     be passed to port 259 on any remote host on either side of the

   For more information, see the Inside Security GmbH security advisory,
   available at


   Although the CERT/CC has not seen any incident activity related to
   this vulnerability, we do recommend that all affected sites upgrade
   their Check Point software as soon as possible.

II. Impact

   An intruder can pass UDP traffic with arbitrary content through the
   firewall on port 259 in violation of implied security policies.

   If an intruder can gain control of a host inside the firewall, he may
   be able to use this vulnerability to tunnel arbitrary traffic across
   the firewall boundary.

   Additionally, even if an intruder does not have control of a host
   inside the firewall, he may be able to use this vulnerability as a
   means of exploiting another vulnerability in software listening
   passively on the internal network.

   Finally, an intruder may be able to use this vulnerability to launch
   certain kinds of denial-of-service attacks.

III. Solutions

   Install a patch from Check Point Software Technologies. More
   information is available in Appendix A.

   Until a patch can be applied, you may be able to reduce your exposure
   to this vulnerability by configuring your router to block access to
   259/UDP at your network perimeter.

Appendix A

Check Point

   Check Point has issued an alert for this vulnerability at


   Download the patch from Check Point's web site:


Appendix B. - References

    1. http://www.inside-security.de/advisories/fw1_rdp.html
    2. http://www.kb.cert.org/vuls/id/310295
    3. http://www.ietf.org/rfc/rfc908.txt
    4. http://www.ietf.org/rfc/rfc1151.txt

   Our thanks to Inside Security GmbH for the information contained in
   their advisory.

   This document was written by Ian A. Finlay. If you have feedback
   concerning this document, please send email to:

          mailto:cert@cert.org?Subject=Feedback CA-2001-17 [VU#310295]

   Copyright 2001 Carnegie Mellon University.

   Revision History
July 09, 2001: Initial Release

Version: PGPfreeware 5.0i for non-commercial use
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