title: A response packet can cause a resolver to terminate when processing an answer containing a CNAME or DNAME
description: Mistaken assumptions about the ordering of records in the answer section of a response containing CNAME or DNAME resource records could lead to a situation in which named would exit with an assertion failure when processing a response in which records occurred in an unusual order. Affects BIND 9.9.9-P6, 9.9.10b1->9.9.10rc1, 9.10.4-P6, 9.10.5b1->9.10.5rc1, 9.11.0-P3, 9.11.1b1->9.11.1rc1, and 9.9.9-S8.
problem types: A server which is performing recursion can be forced to exit with an assertion failure if it can be caused to receive a response containing CNAME or DNAME resource records with certain ordering.  An attacker can cause a denial of service by exploiting this condition.  Recursive resolvers are at highest risk but authoritative servers are theoretically vulnerable if they perform recursion.
affected:
{
product: BIND 9
vendor: ISC
versions:
status: affected, version: 9.9.9-P6, 9.9.10b1->9.9.10rc1, 9.10.4-P6, 9.10.5b1->9.10.5rc1, 9.11.0-P3, 9.11.1b1->9.11.1rc1, and 9.9.9-S8
}
metrics:
cvssV3_0: [
attackComplexity: LOW
attackVector: NETWORK
availabilityImpact: HIGH
baseScore: 7.5
baseSeverity: HIGH
confidentialityImpact: NONE
integrityImpact: NONE
privilegesRequired: NONE
scope: UNCHANGED
userInteraction: NONE
vectorString: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
version: 3.0
]
solutions:  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-P8
BIND 9 version 9.10.4-P8
BIND 9 version 9.11.0-P5
BIND Supported Preview Edition is a special feature preview branch of BIND provided to eligible ISC support customers.
BIND 9 version 9.9.9-S10
New maintenance releases of BIND are also scheduled which contain the fix for this vulnerability.  In addition to the security releases listed above, fixes for this vulnerability are also included in these release candidate versions:
BIND 9 version 9.9.10rc3
BIND 9 version 9.10.5rc3
BIND 9 version 9.11.1rc3
workarounds: None known.