CVE-2016-8864: A problem handling responses containing a DNAME, answer can lead to an assertion failure

Brian Conry bconry at
Tue Nov 1 19:59:15 UTC 2016

CVE-2016-8864: A problem handling responses containing a DNAME
answer can lead to an assertion failure

CVE:                    CVE-2016-8864
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,
Severity:               High
Exploitable:            Remotely


   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").

 ther 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:

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.


   Upgrade to the patched release most closely related to your current
   version of BIND.

   -  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


   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,
   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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Advance Security Notifications, please visit

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