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

[Michael McNally]

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.
(https://lists.isc.org/mailman/listinfo/bind-announce)
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

Description:

   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
   'allow-query').

Impact:

   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:
http://nvd.nist.gov/cvss.cfm?calculator&adv&version=2&vector=(AV:N/AC:L/Au:N/C:N/I:N/A:C)

Workarounds:

   No practical workarounds exist.

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
   http://www.isc.org/downloads.

     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
affected.
       Updated solution section to reflect replacing 9.11.0rc2 with
9.11.0rc3
       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:

   https://www.isc.org/downloads/software-support-policy/openpgp-key

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

Note:

   ISC patches only currently supported versions. When possible we
   indicate EOL versions affected.  (For current information on which
   versions are actively supported, please see
http://www.isc.org/downloads/).

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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