CVE-2016-2088: A response containing multiple DNS cookies causes servers with cookie support enabled to exit with an assertion failure.

Michael McNally mcnally at
Wed Mar 9 21:05:57 UTC 2016

CVE:                   CVE-2016-2088
Document Version:      2.0
Posting date:          09 March 2016
Program Impacted:      BIND
Versions affected:     9.10.0 -> 9.10.3-P3
Severity:              High
Exploitable:           Remotely


   BIND 9.10 has preliminary support for DNS cookies (or source
   identity tokens), a proposed mechanism designed to allow lightweight
   transaction security between a querying party and a nameserver.
   An error in the BIND code implementing support for this optional
   feature permits a deliberately misconstructed packet containing
   multiple cookie options to cause named to terminate with an
   INSIST assertion failure in resolver.c if DNS cookie support is
   enabled in the server.  Only servers with DNS cookie support
   enabled at build time can be affected by this defect; in servers
   which do not have DNS cookie support selected any cookies
   encountered will be ignored as unknown option types.


   Servers which are built with DNS cookie support enabled are
   vulnerable to denial of service if an attacker can cause them
   to receive and process a response that contains multiple cookie

CVSS Score:            7.8
CVSS Vector:           (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:


   Servers which do not have cookie support included are not at
   risk from this vulnerability.

   When BIND 9.10 is built from ISC-supported source, cookie support
   is not selected by default.  In order to be included it must be
   elected using the "--enable-sit" command-line argument when
   running the "configure" script in the top level source directory.
   Operators with affected servers can re-configure and re-build
   BIND without cookie support if they prefer not to upgrade to a
   release containing the fix. However, ISC-provided binary packages
   for Windows do have "--enable-sit" selected.  Server operators
   using the Windows binary packages should upgrade to the corrected

Active exploits:

   No known active exploits.


   Re-configure and re-build BIND without enabling cookie support
   or upgrade to the patched release most closely related to your
   current version of BIND.

   - BIND 9 version 9.10.3-P4

Document Revision History:

   1.0 Advance Notification 02 March 2016
   2.0 Public Disclosure.  09 March 2016

Related Documents:

   See our BIND9 Security Vulnerability Matrix at for a complete listing of
   Security Vulnerabilities and versions affected.

If you'd like more information on ISC Subscription Support and
Advance Security Notifications, please visit

Do you still have questions?  Questions regarding this advisory
should go to security-officer at  To report a new issue,
please encrypt your message using security-officer at's PGP
key which can be found here:

If you are unable to use encrypted email, you may also report new
issues at:


   ISC patches only currently supported versions. When possible we
   indicate EOL versions affected.  (For current information on
   which versions are actively supported, please see

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.

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) 2001-2016 Internet Systems Consortium

More information about the bind-announce mailing list