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             AUSCERT External Security Bulletin Redistribution

                     ESB-2001.181 -- RHSA-2001:052-02
                 FTP iptables vulnerability in 2.4 kernel
                                3 May 2001

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        AusCERT Security Bulletin Summary
        ---------------------------------

Product:                Linux 2.4 Kernel
Vendor:                 Red Hat
Operating System:       Red Hat Linux 7.1
Impact:                 Inappropriate Access
Access Required:        Remote

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                   Red Hat, Inc. Red Hat Security Advisory

Synopsis:          FTP iptables vulnerability in 2.4 kernel
Advisory ID:       RHSA-2001:052-02
Issue date:        2001-04-19
Updated on:        2001-04-19
Product:           Red Hat Linux
Keywords:          FTP iptables ip_conntrack_ftp
Cross references:  
Obsoletes:         
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1. Topic:

A security hole has been found that does not affect the default
configuration of Red Hat Linux, but can affect some custom
configurations of Red Hat Linux 7.1 only.  The bug is specific
to the Linux 2.4 kernel series.

2. Relevant releases/architectures:



3. Problem description:

A vulnerability in iptables "RELATED" connection tracking has been
discovered.  When using iptables to allow FTP "RELATED" connections
through the firewall, carefully constructed PORT commands can open
arbitrary holes in the firewall.

The iptables system is included in the 2.4 kernel series, but not in
the earlier 2.2 kernel series used in Red Hat Linux 6.x and Red Hat
Linux 7.0.

Red Hat Linux 7.1 uses a 2.4 kernel and provides the ip_conntrack_ftp
module that has this bug.  However, Red Hat Linux does not currently
configure iptables (the default firewall configuration uses ipchains
instead), so unless you have explicitly configured iptables and
enabled FTP "RELATED" connections through the firewall, you are not
vulnerable to attack.

4. Solution:

Red Hat will be releasing a kernel with this and other bugs fixed
shortly.  In the meantime, we strongly recommend that users of
iptables not allow FTP "RELATED" connections.

5. Bug IDs fixed (http://bugzilla.redhat.com/bugzilla for more info):



6. RPMs required:



7. Verification:

MD5 sum                           Package Name
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These packages are GPG signed by Red Hat, Inc. for security.  Our key
is available at:
    http://www.redhat.com/corp/contact.html

You can verify each package with the following command:
    rpm --checksig  <filename>

If you only wish to verify that each package has not been corrupted or
tampered with, examine only the md5sum with the following command:
    rpm --checksig --nogpg <filename>

8. References:

http://www.tempest.com.br/advisories/01-2001.html
http://www.securityfocus.com/templates/archive.pike?list=1&mid=177070
http://slashdot.org/comments.pl?sid=01/04/19/047249&cid=36


Copyright(c) 2000, 2001 Red Hat, Inc.

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