CVE-2016-9778: An error handling certain queries using the nxdomain-redirect feature could cause a REQUIRE assertion failure in db.c
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CVE-2016-9778: An error handling certain queries using the nxdomain-redirect feature could cause a REQUIRE assertion failure in db.c

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Article Summary

CVE: CVE-2016-9778

Document version: 2.0

Posting date: 11 Jan 2017

Program impacted: BIND

Versions affected: 9.9.8-S1 -> 9.9.8-S3, 9.9.9-S1 -> 9.9.9-S6, 9.11.0-9.11.0 -> P1

Severity: High (for affected configurations)

Exploitable: Remotely


An error in handling certain queries can cause an assertion failure when a server is using the nxdomain-redirect feature to cover a zone for which it is also providing authoritative service. A vulnerable server could be intentionally stopped by an attacker if it was using a configuration that met the criteria for the vulnerability and if the attacker could cause it to accept a query that possessed the required attributes.

Please note: This vulnerability affects the "nxdomain-redirect" feature, which is one of two methods of handling NXDOMAIN redirection, and is only available in certain versions of BIND.  Redirection using zones of type "redirect" is not affected by this vulnerability.


Only servers which are performing NXDOMAIN redirection using the "nxdomain-redirect" function are potentially vulnerable and then only a subset of those servers. To be affected, a server must be using nxdomain-redirect AND must be redirecting NXDOMAIN responses for a zone for which the server also provides authoritative service; therefore, a purely recursive server is not at risk, either. Successful exploitation of the vulnerability will cause named to stop execution after encountering a REQUIRE assertion failure in db.c, resulting in denial of service to clients.

CVSS 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:


Either provide an ordinary (that is, not redirected) NXDOMAIN for non-existent resource records in zones for which authoritative data is served on the same server, or use redirect zones instead of the nxdomain-redirect feature.

Active exploits: No known active exploits.

Solution: Upgrade to the patched release most closely related to your current version of BIND. These can be downloaded from

  • BIND 9 version 9.11.0-P2

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

  • BIND 9.9.9-S7

Document Revision History:

1.0 Advance Notification, 03 January 2017
1.1 Updated Versions affected to include 9.11.0-P1, 04 January 2017
2.0 Public Announcement, 11 January 2017

Related Documents: See our BIND 9 Security Vulnerability Matrix for a complete listing of Security Vulnerabilities and versions affected.

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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 

ISC Security Vulnerability Disclosure Policy: Details of our current security advisory policy and practice can be found in the ISC Software Defect and Security Vulnerability Disclosure Policy.

This Knowledgebase article is the complete and official security advisory document.

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