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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: 139275 Created: 2017-06-14 08:00 Last Updated: 2017-06-14 20:18 0 Rating/ Voters

Document Version: 
Posting date: 
14 June 2017
Program Impacted: 
Versions affected: 
9.9.10, 9.10.5, 9.11.0->9.11.1, 9.9.10-S1, 9.10.5-S1


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.


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:


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

  • 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 for a complete listing of Security Vulnerabilities and versions affected.

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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's PGP key which can be found here:  If you are unable to use encrypted email, you may also report new issues at:

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 

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This Knowledge Base article is the complete and official security advisory document.

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