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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
Operating System: Windows
UNIX variants (UNIX, Linux, OSX)
Impact/Access: Denial of Service -- Remote/Unauthenticated
CVE Names: CVE-2015-4620
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
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CVE-2015-4620: Specially Constructed Zone Data Can Cause a Resolver to Crash
Author: Michael McNally
Reference Number: AA-01267
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.
Document Version: 2.0
Posting date: 7 July 2015
Program Impacted: BIND
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.
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
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
See our BIND9 Security Vulnerability Matrix at
https://kb.isc.org/article/AA-00913 for a complete listing of Security
Vulnerabilities and versions affected.
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