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[ GLSA 200407-12 ] Linux Kernel: Remote DoS vulnerability with IPTables TCP Handling
From: Tim Yamin <plasmaroo () gentoo org>
Date: Wed, 14 Jul 2004 22:04:06 +0100

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Gentoo Linux Security Advisory                           GLSA 200407-12
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                                            http://security.gentoo.org/
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  Severity: High
     Title: Linux Kernel: Remote DoS vulnerability with IPTables TCP
            Handling
      Date: July 14, 2004
      Bugs: #55694
        ID: 200407-12

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Synopsis
========

A flaw has been discovered in 2.6 series Linux kernels that allows an
attacker to send a malformed TCP packet, causing the affected kernel
to possibly enter an infinite loop and hang the vulnerable machine.

Background
==========

The Linux kernel is responsible for managing the core aspects of a
GNU/Linux system, providing an interface for core system applications
as well as providing the essential structure and capability to access
hardware that is needed for a running system.

Affected packages
=================

    -------------------------------------------------------------------
     Kernel                /    Unaffected    /                Remerge
    -------------------------------------------------------------------
  1  aa-sources ............... >= 2.6.5-r5 ...................... YES
  2  ck-sources ............... >= 2.6.7-r2 ...................... YES
  3  gentoo-dev-sources ....... >= 2.6.7-r7 ..........................
  4  hardened-dev-sources ..... >= 2.6.7-r1 ..........................
  5  hppa-dev-sources ....... >= 2.6.7_p1-r1 .........................
  6  mips-sources ............ *>= 2.6.4-r4 ..........................
     .......................... >= 2.6.7-r1 ..........................
  7  mm-sources ............... >= 2.6.7-r4 ...................... YES
  8  pegasos-dev-sources ...... >= 2.6.7-r1 ..........................
  9  rsbac-dev-sources ........ >= 2.6.7-r1 ..........................
 10  uclinux-sources ........ >= 2.6.7_p0-r1 .........................
 11  usermode-sources ......... >= 2.6.6-r2 ..........................
 12  win4lin-sources .......... >= 2.6.7-r1 ..........................
 13  xbox-sources ............. >= 2.6.7-r1 ..........................
 14  development-sources ...... Vulnerable! ..........................
    -------------------------------------------------------------------
     NOTE: Some kernels are still vulnerable. Users should migrate to
           another kernel if one is available or seek another
           solution such as patching their existing kernel.
    -------------------------------------------------------------------
     NOTE: Packages marked with "Remerge" as "YES" require a re-merge
           even though Portage does not indicate a newer version!
    -------------------------------------------------------------------
     14 affected packages on all of their supported architectures.
    -------------------------------------------------------------------

Description
===========

An attacker can utilize an erroneous data type in the IPTables TCP
option handling code, which lies in an iterator. By making a TCP packet
with a header length larger than 127 bytes, a negative integer would be
implied in the iterator.

Impact
======

By sending one malformed packet, the kernel could get stuck in a loop,
consuming all of the CPU resources and rendering the machine useless,
causing a Denial of Service. This vulnerability requires no local
access.

Workaround
==========

If users do not use the netfilter functionality or do not use any
``--tcp-option'' rules they are not vulnerable to this exploit. Users
that are may remove netfilter support from their kernel or may remove
any ``--tcp-option'' rules they might be using. However, all users are
urged to upgrade their kernels to patched versions.

Resolution
==========

Users are encouraged to upgrade to the latest available sources for
their system:

    # emerge sync
    # emerge -pv your-favorite-sources
    # emerge your-favorite-sources

    # # Follow usual procedure for compiling and installing a kernel.
    # # If you use genkernel, run genkernel as you would do normally.

Availability
============

This GLSA and any updates to it are available for viewing at
the Gentoo Security Website:

    http://security.gentoo.org/glsa/glsa-200407-12.xml

Concerns?
=========

Security is a primary focus of Gentoo Linux and ensuring the
confidentiality and security of our users machines is of utmost
importance to us. Any security concerns should be addressed to
security () gentoo org or alternatively, you may file a bug at
http://bugs.gentoo.org.

License
=======

Copyright 2004 Gentoo Foundation, Inc; referenced text
belongs to its owner(s).

The contents of this document are licensed under the
Creative Commons - Attribution / Share Alike license.

http://creativecommons.org/licenses/by-sa/1.0

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