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Gentoo Linux Security Advisory                           GLSA 200407-12
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                                             https://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. Usersthat 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:

     https://security.gentoo.org/glsa/200407-12

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
https://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.

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