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             AUSCERT External Security Bulletin Redistribution

        CVE-2015-4620: Specially Constructed Zone Data Can Cause a
                     Resolver to Crash when Validating
                                8 July 2015


        AusCERT Security Bulletin Summary

Product:           BIND
Publisher:         ISC
Operating System:  Windows
                   UNIX variants (UNIX, Linux, OSX)
Impact/Access:     Denial of Service -- Remote/Unauthenticated
Resolution:        Patch/Upgrade
CVE Names:         CVE-2015-4620  

Original Bulletin: 

Comment: This advisory references vulnerabilities in products which run on 
         platforms other than Windows. It is recommended that administrators
         running BIND check for an updated version of the software for their
         operating system.

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CVE-2015-4620: Specially Constructed Zone Data Can Cause a Resolver to Crash 
when Validating

Author: Michael McNally

Reference Number: AA-01267

Views: 859

Created: 2015-06-16 19:57

Last Updated: 2015-07-07 18:15

0 Rating/ Voters

An attacker who can cause a validating resolver to query a zone containing 
specifically constructed contents can cause that resolver to fail an assertion
and terminate due to a defect in validation code.

CVE: CVE-2015-4620

Document Version: 2.0

Posting date: 7 July 2015

Program Impacted: BIND

Versions affected:

BIND 9.7.1 -> 9.7.7, 9.8.0 -> 9.8.8, 9.9.0 -> 9.9.7, 9.10.0 -> 9.10.2-P1.

Severity: Critical

Exploitable: Remotely


A very uncommon combination of zone data has been found that triggers a bug in
BIND, with the result that named will exit with a "REQUIRE" failure in name.c
when validating the data returned in answer to a recursive query.

This means that a recursive resolver that is performing DNSSEC validation can
be deliberately stopped by an attacker who can cause the resolver to perform a
query against a maliciously-constructed zone.


A recursive resolver that is performing DNSSEC validation can be deliberately
terminated by any attacker who can cause a query to be performed against a 
maliciously constructed zone. This will result in a denial of service to 
clients who rely on that resolver.

DNSSEC validation is only performed by a recursive resolver if it has 
"dnssec-validation auto;" in its configuration or if it has a root trust 
anchor defined and has "dnssec-validation yes;" set (either by accepting the 
default or via an explicitly set value of "yes".) By default ISC BIND 
recursive servers will not validate. (However, ISC defaults may have been 
changed by your distributor.)

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: 


Disabling DNSSEC validation prevents exploitation of this defect but is not 
generally recommended. The recommended solution is to upgrade to a patched 

Active exploits:

There are no known active exploits at this time.

Solution: Upgrade to the patched release most closely related to your current
version of BIND:

BIND 9 version 9.9.7-P1

BIND 9 version 9.10.2-P2

Acknowledgements: ISC would like to thank Breno Silveira Soares of Servio 
Federal de Processamento de Dados (SERPRO) for discovering and reporting this

Document Revision History:

1.0 Phase One: Advance Notification 23 June, 2015

1.1 Phase Two: Notification to BIND Packagers 29 June, 2015

1.2 Revised public release date (to 7 July 2015) and re-notified Phase One and
Phase Two recipients: 30 June, 2015

2.0 Phase Three: Public Disclosure, 7 July 2015

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

This Knowledge Base article https://kb.isc.org/article/AA-01267 is the 
complete and official security advisory document.

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