title: A buffer boundary check assertion in rdataset.c can fail incorrectly during zone transfer
description: In ISC BIND9 versions BIND 9.11.14 -> 9.11.19, BIND 9.14.9 -> 9.14.12, BIND 9.16.0 -> 9.16.3, BIND Supported Preview Edition 9.11.14-S1 -> 9.11.19-S1: Unless a nameserver is providing authoritative service for one or more zones and at least one zone contains an empty non-terminal entry containing an asterisk ("*") character, this defect cannot be encountered. A would-be attacker who is allowed to change zone content could theoretically introduce such a record in order to exploit this condition to cause denial of service, though we consider the use of this vector unlikely because any such attack would require a significant privilege level and be easily traceable.
problem types: The asterisk character ("*") is allowed in DNS zone files, where it is most commonly present as a wildcard at a terminal node of the Domain Name System graph. However, the RFCs do not require and BIND does not enforce that an asterisk character be present only at a terminal node.  A problem can occur when an asterisk is present in an empty non-terminal location within the DNS graph. If such a node exists, after a series of queries, named can reach an inconsistent state that results in the failure of an assertion check in rbtdb.c, followed by the program exiting due to the assertion failure.  Versions affected: BIND 9.11.14 -> 9.11.19, BIND 9.14.9 -> 9.14.12, BIND 9.16.0 -> 9.16.3. Also, versions 9.11.14-S1 -> 9.11.19-S1 of BIND Supported Preview Edition
affected:
{
product: BIND9
vendor: ISC
versions:
status: affected, version: 9.11.14 through versions before 9.11.20
status: affected, version: 9.16.0 through versions before 9.16.4
status: affected, version: 9.11.14-S1 through versions before 9.11.20-S1
status: affected, version: 9.14.9 through versions 9.14.12
}
metrics:
cvssV3_1: [
attackComplexity: LOW
attackVector: NETWORK
availabilityImpact: HIGH
baseScore: 4.9
baseSeverity: MEDIUM
confidentialityImpact: NONE
integrityImpact: NONE
privilegesRequired: HIGH
scope: UNCHANGED
userInteraction: NONE
vectorString: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
version: 3.1
]
solutions: Upgrade to the patched release most closely related to your current version of BIND:
BIND 9.11.20
BIND 9.16.4
BIND Supported Preview Edition is a special feature preview branch of BIND provided to eligible ISC support customers.
BIND 9.11.20-S1
workarounds: None