Hash: SHA1

             AUSCERT External Security Bulletin Redistribution

          CVE-2012-3955: Reducing the expiration time for an IPv6
                    lease may cause the server to crash
                             14 September 2012


        AusCERT Security Bulletin Summary

Product:           DHCP
Publisher:         Internet Systems Consortium
Operating System:  Windows
                   UNIX variants (UNIX, Linux, OSX)
Impact/Access:     Denial of Service -- Remote/Unauthenticated
Resolution:        Patch/Upgrade
CVE Names:         CVE-2012-3955  

Original Bulletin: 

- --------------------------BEGIN INCLUDED TEXT--------------------

CVE-2012-3955: Reducing the expiration time for an IPv6 lease may cause the 
server to crash

Author: Cathy Almond 
Reference Number: AA-00779 
Created: 2012-08-23 15:08 
Last Updated: 2012-09-12 16:26	

CVE: CVE-2012-3955
Document Version: 2.0
Posting date: 12 September 2012
Program Impacted: ISC DHCP 4
Versions affected: 4.1.x, 4.2.x
Severity: Medium
Exploitable: From networks permitted to send requests to the DHCP server.


ISC has discovered that reducing the expiration time for an active IPv6 lease 
may cause the server to crash.

Please Note: Versions of ISC DHCP 4.0 may also be affected, but these branches 
are beyond their "end of life" (EOL) and no longer receive testing or security 
fixes from ISC. For current information on which versions are actively 
supported, please see http://www.isc.org/software/dhcp/versions.


Affected servers can terminate unexpectedly, resulting in a denial of service 
condition for clients.

CVSS Score:  5.7

CVSS Equation:  (AV:A/AC:M/Au:N/C:N/I:N/A:C)

For more information on the Common Vulnerability Scoring System and to obtain 
your specific environmental score please visit: 


ISC recommends setting a value for the default-lease-time option in the 
configuration file, and not reducing it once set.

Active exploits:

No known active exploits.

Solution:  Upgrade to the updated release most closely related to your current 
version of DHCP.  These can be downloaded from 

    ISC DHCP version 4.1-ESV-R7
    ISC DHCP version 4.2.4-P2

Acknowledgements: ISC would like to thank Glen Eustace of Massey University, 
New Zealand for finding this issue.

Document Revision History:

1.0 - 4 Sept. 2012 Advance Notification to Phase 1
1.1 - 11 Sept. 2012 Phase 2 & 3 notified
2.0 - 12 Sept. 2012 Phase 4 - Public Released

Related Documents:

If you'd like more information on our Forum or product support please visit 
www.isc.org/software/guild or www.isc.org/support.

Do you still have questions?  Questions regarding this advisory should go to 

Note: ISC patches only currently supported versions. When possible we indicate 
EOL versions affected.

ISC Security Vulnerability Disclosure Policy:  Details of our current security 
advisory policy and practice can be found here: 

This Knowledge Base article https://kb.isc.org/article/AA-00779 is the complete 
and official security advisory document.  There is also a summary article 
located on our website and linking to here: 

Legal Disclaimer:
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No warranty or guarantee of any kind is expressed in this notice and none 
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without limitation, any implied warranty of merchantability, fitness for a 
particular purpose, absence of hidden defects, or of non-infringement. Your use 
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own risk. ISC may change this notice at any time.  A stand-alone copy or 
paraphrase of the text of this document that omits the document URL is an 
uncontrolled copy. Uncontrolled copies may lack important information, be out 
of date, or contain factual errors.

(c) 2001-2012 Internet Systems Consortium

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