[dns-operations] CVE-2016-2776: Assertion Failure in buffer.c While Building Responses to a Specifically Constructed Request

Michael McNally mcnally at isc.org
Tue Sep 27 17:18:58 UTC 2016

To whom it may concern:

Today ISC announced a serious denial-of-service vector affecting all
prior versions of BIND 9.

The new vulnerability has been designated CVE-2016-2776.

Authoritative and recursive servers are both vulnerable and
countermeasures via server configuration are not practical for
a working server.  All BIND server operators are advised to read
the vulnerability announcement and upgrade to fixed versions.

BIND vulnerabilities are generally announced via the "bind-announce"
public list operated by ISC.
We are additionally notifying this list because of the severity of
this particular vulnerability.

Michael McNally
ISC Security Officer


CVE:                   CVE-2016-2776
Document Version:      2.0
Posting date:          2016-09-27
Program Impacted:      BIND
Versions affected:     9.0.x -> 9.8.x, 9.9.0->9.9.9-P2, 9.9.3-S1->9.9.9-S3,
                       9.10.0->9.10.4-P2, 9.11.0a1->9.11.0rc1
Severity:              High
Exploitable:           Remotely


   Testing by ISC has uncovered a critical error condition which
   can occur when a nameserver is constructing a response.  A defect
   in the rendering of messages into packets can cause named to
   exit with an assertion failure in buffer.c while constructing a
   response to a query that meets certain criteria.

   This assertion can be triggered even if the apparent source
   address isn't allowed to make queries (i.e. doesn't match


   All servers are vulnerable if they can receive request packets from
any source.

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:


   No practical workarounds exist.

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 9.9.9-P3
     BIND 9 version 9.10.4-P3
     BIND 9 version 9.11.0rc3

   BIND 9 Supported Preview edition is a feature preview version of
   BIND provided exclusively to eligible ISC Support customers.

     BIND 9 version 9.9.9-S5

Document Revision History:

   1.0 Advance Notification 2016-09-14
   1.1 Added information about the Stable Preview release to versions
       Updated solution section to reflect replacing 9.11.0rc2 with
       and 9.9.9-S4 with 9.9.9-S5.
   2.0 Posting date changed and public disclosure, 2016-09-28

Related Documents:

   See our BIND9 Security Vulnerability Matrix at
   https://kb.isc.org/article/AA-00913 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 http://www.isc.org/support/.

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


If you are unable to use encrypted email, you may also report new
issues at: https://www.isc.org/community/report-bug/.


   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: https://kb.isc.org/article/AA-00861

This Knowledge Base article https://kb.isc.org/article/AA-01419 is
the complete and official security advisory document.

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