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TUCoPS :: Linux :: Gentoo :: tb12973.htm

DenyHosts: Denial of Service



DenyHosts: Denial of Service
DenyHosts: Denial of Service



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Gentoo Linux Security Advisory                           GLSA 200710-14
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http://security.gentoo.org/ 
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  Severity: Normal
     Title: DenyHosts: Denial of Service
      Date: October 13, 2007
      Bugs: #181213
        ID: 200710-14

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Synopsis
=======
DenyHosts does not correctly parse log entries, potentially causing a
remote Denial of Service.

Background
=========
DenyHosts is designed to monitor SSH servers for repeated failed login
attempts.

Affected packages
================
    -------------------------------------------------------------------
     Package              /  Vulnerable  /                  Unaffected
    -------------------------------------------------------------------
  1  app-admin/denyhosts      < 2.6-r1                       >= 2.6-r1

Description
==========
Daniel B. Cid discovered that DenyHosts used an incomplete regular
expression to parse failed login attempts, a different issue than GLSA
200701-01.

Impact
=====
A remote unauthenticated attacker can add arbitrary hosts into the
blacklist, including the "all" keyword, by submitting specially crafted
version identification strings to the SSH server banner. An attacker
may use this to prevent legitimate users from accessing a host
remotely.

Workaround
=========
There is no known workaround at this time.

Resolution
=========
All DenyHosts users should upgrade to the latest version:

    # emerge --sync
    # emerge --ask --oneshot --verbose ">=app-admin/denyhosts-2.6-r1"

References
=========
  [ 1 ] CVE-2007-4323
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2007-4323 

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

http://security.gentoo.org/glsa/glsa-200710-14.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 2007 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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