[Full-disclosure] [ GLSA 200609-17 ] OpenSSH: Denial of Service

[Sune Kloppenborg Jeppesen]

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Gentoo Linux Security Advisory                           GLSA 200609-17
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                                            http://security.gentoo.org/
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  Severity: Normal
     Title: OpenSSH: Denial of Service
      Date: September 27, 2006
      Bugs: #148228
        ID: 200609-17

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Synopsis
========

A flaw in the OpenSSH daemon allows remote unauthenticated attackers to
cause a Denial of Service.

Background
==========

OpenSSH is a free suite of applications for the SSH protocol, developed
and maintained by the OpenBSD project.

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

    -------------------------------------------------------------------
     Package           /   Vulnerable   /                   Unaffected
    -------------------------------------------------------------------
  1  net-misc/openssh      < 4.3_p2-r5                    >= 4.3_p2-r5

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

Tavis Ormandy of the Google Security Team discovered a Denial of
Service vulnerability in the SSH protocol version 1 CRC compensation
attack detector.

Impact
======

A remote unauthenticated attacker may be able to trigger excessive CPU
usage by sending a pathological SSH message, denying service to other
legitimate users or processes.

Workaround
==========

The system administrator may disable SSH protocol version 1 in
/etc/ssh/sshd_config.

Resolution
==========

All OpenSSH users should upgrade to the latest version:

    # emerge --sync
    # emerge --ask --oneshot --verbose ">=net-misc/openssh-4.3_p2-r3"

References
==========

  [ 1 ] CVE-2006-4924
        http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-4924

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

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

  http://security.gentoo.org/glsa/glsa-200609-17.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 at gentoo.org or alternatively, you may file a bug at
http://bugs.gentoo.org.

License
=======

Copyright 2006 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/2.5
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