Date: 10 March 2016
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AUSCERT External Security Bulletin Redistribution
CVE-2016-2088: A response containing multiple DNS cookies causes servers
with cookie support enabled to exit with an assertion failure.
10 March 2016
AusCERT Security Bulletin Summary
Operating System: UNIX variants (UNIX, Linux, OSX)
Impact/Access: Denial of Service -- Remote/Unauthenticated
CVE Names: CVE-2016-2088
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CVE-2016-2088: A response containing multiple DNS cookies causes servers with
cookie support enabled to exit with an assertion failure.
Author: Michael McNally
Reference Number: AA-01351
Created: 2016-03-09 18:30
Last Updated: 2016-03-09 19:49
Document Version: 2.0
Posting date: 09 March 2016
Program Impacted: BIND
Versions affected: 9.10.0 -> 9.10.3-P3
BIND 9.10 has preliminary support for DNS cookies (or source identity tokens),
a proposed mechanism designed to allow lightweight transaction security
between a querying party and a nameserver. An error in the BIND code
implementing support for this optional feature permits a deliberately
misconstructed packet containing multiple cookie options to cause named to
terminate with an INSIST assertion failure in resolver.c if DNS cookie support
is enabled in the server. Only servers with DNS cookie support enabled at
build time can be affected by this defect; in servers which do not have DNS
cookie support selected any cookies encountered will be ignored as unknown
Servers which are built with DNS cookie support enabled are vulnerable to
denial of service if an attacker can cause them to receive and process a
response that contains multiple cookie options.
CVSS Score: 7.8
CVSS Vector: (AV:N/AC:L/Au:N/C:N/I:N/A:C)
For more information on the Common Vulnerability Scoring System and to obtain
your specific environmental score please visit:
Servers which do not have cookie support included are not at risk from this
When BIND 9.10 is built from ISC-supported source, cookie support is not
selected by default. In order to be included it must be elected using the
"--enable-sit" command-line argument when running the "configure" script in
the top level source directory. Operators with affected servers can
re-configure and re-build BIND without cookie support if they prefer not to
upgrade to a release containing the fix. However, ISC-provided binary packages
for Windows do have "--enable-sit" selected. Server operators using the
Windows binary packages should upgrade to the corrected version.
No known active exploits.
Solution: Re-configure and re-build BIND without enabling cookie support or
upgrade to the patched release most closely related to your current version of
BIND 9 version 9.10.3-P4
Document Revision History:
1.0 Advance Notification 02 March 2016
2.0 Public Disclosure. 09 March 2016
See our BIND9 Security Vulnerability Matrix at
https://kb.isc.org/article/AA-00913 for a complete listing of Security
Vulnerabilities and versions affected.
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