CVE-2016-9147: An error handling a query response containing inconsistent DNSSEC information could cause an assertion failure
Document version: 2.0
Posting date: 11 Jan 2017
Program impacted: BIND
Versions affected: 9.9.9-P4, 9.9.9-S6, 9.10.4-P4, 9.11.0-P1
Depending on the type of query and the EDNS options in the query they receive, DNSSEC-enabled authoritative servers are expected to include RRSIG and other RRsets in their responses to recursive servers. DNSSEC-validating servers will also make specific queries for DS and other RRsets. Whether DNSSEC-validating or not, an error in processing malformed query responses that contain DNSSEC-related RRsets that are inconsistent with other RRsets in the same query response can trigger an assertion failure. Although 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.
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 Why does my authoritative-only nameserver try to query the root nameservers?). There are several variations of malformed query response that can cause an assertion failure, some of which will trigger a failure on recursive servers that are not DNSSEC-validating.
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: None known.
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 https://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 1.1 Updated Versions affected to include 9.9.9-S6 and Solution to include 9.9.9-S7, 09 January 2017 2.0 Public Announcement, 11 January 2017
See our BIND 9 Security Vulnerability Matrix for a complete listing of security vulnerabilities and versions affected.
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ISC patches only currently supported versions. When possible we indicate EOL versions affected. (For current information on which versions are actively supported, please see https://www.isc.org/downloads/).
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