ISC Security Advisory: BIND 9 servers using DNS64 can be crashed by a crafted query

Michael McNally mcnally at
Tue Dec 4 18:47:32 UTC 2012

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

CVE:                     CVE-2012-5688
Document Version:        2.0
Posting date:            04 Dec 2012
Program Impacted:        BIND
Versions affected:       9.8.0->9.8.4, 9.9.0->9.9.2
Severity:                Critical
Exploitable:             Remotely


   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.


   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


   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 security-officer at

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

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