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CVE-2017-3135: Combination of DNS64 and RPZ Can Lead to Crash
Author: Brian Conry Reference Number: AA-01453 Views: 45158 Created: 2017-02-08 17:44 Last Updated: 2017-02-09 14:07 0 Rating/ Voters

Some configurations using both DNS64 and RPZ can lead to an INSIST assertion failure or a NULL pointer read; in either case named will terminate.

Document Version: 
2.1
Posting date: 
08 Feb 2017
Program Impacted: 
BIND
Versions affected: 
9.8.8, 9.9.3-S1 -> 9.9.9-S7, 9.9.3 -> 9.9.9-P5, 9.9.10b1, 9.10.0 -> 9.10.4-P5, 9.10.5b1, 9.11.0 -> 9.11.0-P2, 9.11.1b1
Severity: 
High, for servers with specific configurations
Exploitable: 
Remotely, but only affecting servers with specific configurations

Description:

Under some conditions when using both DNS64 and RPZ to rewrite query responses, query processing can resume in an inconsistent state leading to either an INSIST assertion failure or an attempt to read through a NULL pointer.

Impact:

Servers utilizing both DNS64 and RPZ are potentially susceptible to encountering this condition.  When this condition occurs, it will result in either an INSIST assertion failure (and subsequent abort) or an attempt to read through a NULL pointer.  On most platforms a NULL pointer read leads to a segmentation fault (SEGFAULT), which causes the process to be terminated.

Only servers which are configured to simultaneously use both Response Policy Zones (RPZ) and DNS64 (a method for synthesizing AAAA records from A records) can be affected by this vulnerability.

CVSS Score:  7.5

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

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:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Workarounds:

While it is possible to avoid the condition by removing either DNS64 or RPZ from the configuration, or by carefully restricting the contents of the policy zone, for an affected configuration the most practical and safest course of action is to upgrade to a version of BIND without this vulnerability.

Active exploits:

No known active exploits.

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 9.9.9-P6
  • BIND 9 version 9.10.4-P6
  • BIND 9 version 9.11.0-P3

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

  • BIND 9 version 9.9.9-S8

Acknowledgements: ISC would like to thank Ramesh Damodaran(Infoblox) and Aliaksandr Shubnik (Infoblox) for reporting the issue and assisting us in the investigation.

Document Revision History:

1.0 Advance Notification 01 Feb, 2017
2.0 Public Announcement 08 Feb, 2017
2.1 Updated Versions Affected to include 9.8.8. 09 Feb, 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-01453 is the complete and official security advisory document.

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