ISC Security Advisory: BIND 9 servers using DNS64 can be crashed by a crafted query
mcnally at isc.org
Tue Dec 4 18:47:32 UTC 2012
A specific query can cause BIND nameservers using DNS64 to exit with a REQUIRE assertion failure.
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
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
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 http://www.isc.org/software/bind/versions.
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.
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)
Japanese Translation: https://kb.isc.org/article/AA-00832
Spanish Translation: https://kb.isc.org/article/AA-00834
German Translation: https://kb.isc.org/article/AA-00833
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 www.isc.org/software/guild or www.isc.org/support.
Do you still have questions? Questions regarding this advisory
should go to security-officer at isc.org
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-00828
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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