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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
Publisher: Internet Systems Consortium
Operating System: Windows
UNIX variants (UNIX, Linux, OSX)
Impact/Access: Denial of Service -- Remote/Unauthenticated
CVE Names: CVE-2012-3955
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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
Document Version: 2.0
Posting date: 12 September 2012
Program Impacted: ISC DHCP 4
Versions affected: 4.1.x, 4.2.x
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.
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
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:
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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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