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ESB-2016.0651 - [Win][UNIX/Linux] BIND: Denial of service - Remote/unauthenticated

Date: 10 March 2016

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             AUSCERT External Security Bulletin Redistribution

                               ESB-2016.0651
 CVE-2016-2088: A response containing multiple DNS cookies causes servers
      with cookie support enabled to exit with an assertion failure.
                               10 March 2016

===========================================================================

        AusCERT Security Bulletin Summary
        ---------------------------------

Product:           BIND
Publisher:         ISC
Operating System:  UNIX variants (UNIX, Linux, OSX)
                   Windows
Impact/Access:     Denial of Service -- Remote/Unauthenticated
Resolution:        Patch/Upgrade
CVE Names:         CVE-2016-2088  

Original Bulletin: 
   https://kb.isc.org/article/AA-01351

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

Author: Michael McNally 

Reference Number: AA-01351 

Views: 2475 

Created: 2016-03-09 18:30 

Last Updated: 2016-03-09 19:49 

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

Description:

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.

Impact:

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 options.

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

Workarounds:

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 version.

Active exploits:

No known active exploits.

Solution: 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 
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@isc.org. To report a new issue, please encrypt your message 
using security-officer@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-00861/164/ISC-Software-Defect-and-Security-Vulnerability-Disclosure-Policy.html

This Knowledge Base article https://kb.isc.org/article/AA-01351 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.

 2001-2016 Internet Systems Consortium

Please help us to improve the content of our knowledge base by letting us know
below how we can improve this article.

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don't submit it here as article feedback.

For assistance with problems and questions for which you have not been able to
find an answer in our Knowledge Base, we recommend searching our community 
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===========================================================================
Australian Computer Emergency Response Team
The University of Queensland
Brisbane
Qld 4072

Internet Email: auscert@auscert.org.au
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