Knowledge Base ISC Main Website Ask a Question/Contact ISC
CVE-2012-5688: BIND 9 servers using DNS64 can be crashed by a crafted query
Author: Michael McNally Reference Number: AA-00828 Views: 25525 Created: 2012-11-19 23:03 Last Updated: 2012-12-04 18:28 0 Rating/ Voters

A specific query can cause BIND nameservers using DNS64 to exit with a REQUIRE assertion failure.

Document Version:          
Posting date: 
04 Dec 2012
Program Impacted: 
Versions affected: 
9.8.0->9.8.4, 9.9.0->9.9.2


BIND 9 nameservers using the DNS64 IPv6 transition mechanism are vulnerable to a software defect that allows a crafted query to crash the server with a REQUIRE assertion failure.  Remote exploitation of this defect can be achieved without extensive effort, resulting in a denial-of-service (DoS) vector against affected servers.

Please Note: Support for DNS64 was added to BIND 9 in version 9.8.0.  Therefore BIND 9 versions prior to 9.8.0 cannot be affected by this bug.  Also, nameservers running versions 9.8.0 and greater can only be affected if DNS64 is turned on using the "dns64" configuration statement. If you are not using DNS64 you are not at risk.

For current information on which versions are actively supported, please see


Any BIND 9 nameserver configured to use DNS64 is vulnerable to this defect and can be crashed by any client machine from which it accepts queries.

CVSS Score:  7.8

CVSS Equation:  (AV:N/AC:L/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:


Only BIND 9 servers which are configured to use DNS64 are vulnerable.  For those servers, disallowing queries from untrusted clients (a recommended practice in any case) will slightly mitigate a server's exposure, but no workarounds are available which will completely protect an affected server against exploitation of this bug.  If you are using DNS64 either disable it or upgrade to a fixed version.

Active exploits:

No known active exploits.

Solution:  Upgrade to the patched release most closely related to your current version of BIND. These can all be downloaded from

  • BIND 9 version 9.8.4-P1
  • BIND 9 version 9.9.2-P1

Acknowledgements:  ISC would like to thank BlueCat Networks for bringing this defect to our attention.

Document Revision History:

1.0 - 27 November 2012 Advance Notification to Phase One.
1.1 - 03 December 2012 Notification to Phase Two and Phase Three
2.0 - 04 December 2012 Notification to Phase Four (Public)

Related Documents:

Japanese Translation:

Spanish Translation:

German Translation:

See our BIND Security Matrix for a complete listing of Security Vulnerabilities and versions affected.

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

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.

© 2001-2018 Internet Systems Consortium

For assistance with problems and questions for which you have not been able to find an answer in our Knowledge Base, we recommend searching our community mailing list archives and/or posting your question there (you will need to register there first for your posts to be accepted). The bind-users and the dhcp-users lists particularly have a long-standing and active membership.

ISC relies on the financial support of the community to fund the development of its open source software products. If you would like to support future product evolution and maintenance as well having peace of mind knowing that our team of experts are poised to provide you with individual technical assistance whenever you call upon them, then please consider our Professional Subscription Support services - details can be found on our main website.

  • There is no feedback for this article
Quick Jump Menu