CVE-2016-9131: A malformed response to an ANY query can cause an assertion failure during recursion

AA-01439

Document Version: 
2.0
Posting date: 
11 Jan 2017
Program Impacted: 
BIND
Versions affected: 
9.4.0 -> 9.6-ESV-R11-W1, 9.8.5 -> 9.8.8, 9.9.3 -> 9.9.9-P4, 9.9.9-S1 -> 9.9.9-S6, 9.10.0 -> 9.10.4-P4, 9.11.0 -> 9.11.0-P1
Severity: 
High
Exploitable: 
Remotely

Description:

A malformed query response received by a recursive server in response to a query of RTYPE ANY could trigger an assertion failure while named is attempting to add the RRs in the query response to the cache.  While the combination of properties which triggers the assertion should not occur in normal traffic, it is potentially possible for the assertion to be triggered deliberately by an attacker sending a specially-constructed answer having the required properties, after having engineered a scenario whereby an ANY query is sent to the recursive server for the target QNAME.  A recursive server will itself only send a query of type ANY if it receives a client query of type ANY for a QNAME for which it has no RRsets at all in cache, otherwise it will respond to the client with the the RRsets that it has available.

Impact:

This vulnerability occurs during the processing of an answer packet received in response to a query.  As a result, recursive servers are at the greatest risk; authoritative servers are at risk only to the extent that they perform a limited set of queries (for example, in order to do zone service - see https://kb.isc.org/article/AA-00914/55/Why-does-my-authoritative-only-nameserver-try-to-query-the-root-nameservers.html).

Successful exploitation of this vulnerability will cause named to encounter an assertion failure and stop executing, resulting in denial of service to clients.

CVSS Score:  7.5

CVSS 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:

The use of external packet filtering to drop client queries of RTYPE=ANY should prevent exploitation of this vulnerability.

Active exploits:

No known active exploits.

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-P5
  • BIND 9 version 9.10.4-P5
  • 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 version 9.9.9-S7

Document Revision History:

1.0 Advance Notification, 03 January 2017
2.0 Public Announcement, 11 January 2017

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-01439 is the complete and official security advisory document.

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