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

AA-01434


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.

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