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CVE-2016-8864: A problem handling responses containing a DNAME answer can lead to an assertion failure
Author: Michael McNally Reference Number: AA-01434 Views: 28302 Created: 2016-11-01 17:47 Last Updated: 2016-11-01 19:31 0 Rating/ Voters


Document Version: 
2.0
Posting date: 
1 November 2016
Program Impacted: 
BIND
Versions affected: 
9.0.x -> 9.8.x, 9.9.0 -> 9.9.9-P3, 9.9.3-S1 -> 9.9.9-S5, 9.10.0 -> 9.10.4-P3, 9.11.0
Severity: 
High
Exploitable: 
Remotely

Description:

A defect in BIND's handling of responses containing a DNAME answer can cause a resolver to exit after encountering an assertion failure in db.c or resolver.c

Impact:

During processing of a recursive response that contains a DNAME record in the answer section, BIND can stop execution after encountering an assertion error in resolver.c (error message: "INSIST((valoptions & 0x0002U) != 0) failed") or db.c (error message: "REQUIRE(targetp != ((void *)0) && *targetp == ((void *)0)) failed").

A server encountering either of these error conditions will stop, resulting in denial of service to clients.  The risk to authoritative servers is minimal; recursive servers are chiefly at risk.

CVSSv3 Score:  7.5

CVSSv3 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:

None known.

Active exploits:

No known active exploits but a query which could trigger the crash was briefly discussed on a public mailing list before the domain owner pulled the record causing the problem.

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-P4
  • BIND 9 version 9.10.4-P4
  • BIND 9 version 9.11.0-P1

BIND 9 Supported Preview edition is a feature preview version of BIND provided exclusively to eligible ISC Support customers.

  • BIND 9 version 9.9.9-S6

Acknowledgements: ISC would like to thank Tony Finch (University of Cambridge), Marco Davids (SIDN Labs) and others for reporting and extending our understanding of the issue.

Document Revision History:

1.0 Advance Notification 21 October, 2016
1.1 Updated versions affected; Updated Acknowledgements.  27 October, 2016
2.0 Public Announcement, 1 November, 2016

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-01434 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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