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CVE-2017-3140: An error processing RPZ rules can cause named to loop endlessly after handling a query
Author: Michael McNally Reference Number: AA-01495 Views: 63451 Created: 2017-06-14 08:00 Last Updated: 2017-06-14 20:18 0 Rating/ Voters

Document Version: 
2.0
Posting date: 
14 June 2017
Program Impacted: 
BIND
Versions affected: 
9.9.10, 9.10.5, 9.11.0->9.11.1, 9.9.10-S1, 9.10.5-S1
Severity:
Medium
Exploitable: 
Remotely

Description:

If named is configured to use Response Policy Zones (RPZ) an error processing some rule types can lead to a condition where BIND will endlessly loop while handling a query.

Impact:

A server is potentially vulnerable to degradation of service if

  1. the server is configured to use RPZ,
  2. the server uses NSDNAME or NSIP policy rules, and
  3. an attacker can cause the server to process a specific query

Successful exploitation of this condition will cause named to enter a state where it continues to loop while processing the query without ever reaching an end state. While in this state, named repeatedly queries the same sets of authoritative nameservers and this behavior will usually persist indefinitely beyond the normal client query processing timeout. By triggering this condition multiple times, an attacker could cause a deliberate and substantial degradation in service.

Operators of servers that meet the above conditions 1. and 2. may also accidentally encounter this defect during normal operation.  It is for this reason that the decision was made to issue this advisory despite its low CVSS score.

CVSS Score:  3.7

CVSS Vector:  CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L

For more information on the Common Vulnerability Scoring System and to obtain your specific environmental score please visit: https://www.first.org/cvss/calculator/3.0#CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L

Workarounds:

Only the NSDNAME and NSIP RPZ rule types can cause this condition to occur.  You can work around this vulnerability if you are able to express your desired policy while avoiding NSDNAME or NSIP rules, otherwise it is advised that you upgrade to a version which corrects the defect.

Active exploits:

No known active exploits but we have received reports of servers accidentally encountering this defect during operation.

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 9.9.10-P1
  • BIND 9 version 9.10.5-P1
  • BIND 9 version 9.11.1-P1

BIND Supported Preview Edition is a special feature preview branch of BIND provided to eligible ISC support customers.

  • BIND 9 version 9.9.10-S2
  • BIND 9 version 9.10.5-S2

Acknowledgements: ISC would like to thank Oli Schacher of Switch for bringing this defect to our attention.

Document Revision History:

1.0 Advance Notification 06 June, 2017
2.0 Public Announcement 14 June, 2017

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.orgTo 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-01495 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.


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