ISC Security Advisory: Reducing the Expiration Time For an IPv6 Lease May Cause the Server to Crash

Michael McNally mcnally at
Wed Sep 12 18:40:14 UTC 2012


  This email advisory is provided for your information. The most
  up to date advisory information will always be at: please use this URL for the
  most up to date advisory information.


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

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


   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.


   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


   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 or

Do you still have questions?  Questions regarding this advisory
should go to security-officer at

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 is
the complete and official security advisory document.  There is
also a summary article located on our website and linking to here:

Legal Disclaimer: 

   Internet Systems Consortium (ISC) is providing this notice on
   an "AS IS" basis. No warranty or guarantee of any kind is expressed
   in this notice and none should be implied. ISC expressly excludes
   and disclaims any warranties regarding this notice or materials
   referred to in this notice, including, without limitation, any
   implied warranty of merchantability, fitness for a particular
   purpose, absence of hidden defects, or of non-infringement. Your
   use or reliance on this notice or materials referred to in this
   notice is at your 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

More information about the dhcp-announce mailing list