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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: 74828 Created: 2016-11-01 17:47 Last Updated: 2016-11-01 19:31 0 Rating/ Voters

Document Version: 
Posting date: 
1 November 2016
Program Impacted: 
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


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


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:


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

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

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

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