description: Versions affected: BIND 9.18.0 When a vulnerable version of named receives a series of specific queries, the named process will eventually terminate due to a failed assertion check.
problem types: We refactored the RFC 8198 Aggressive Use of DNSSEC-Validated Cache feature (synth-from-dnssec) for the new BIND 9.18.0 stable release, and changed the default so that is now automatically enabled for dnssec-validating resolvers. Subsequently it was found that repeated patterns of specific queries to servers with this feature enabled could cause an INSIST failure in query.c:query_dname which causes named to terminate unexpectedly. The vulnerability affects BIND resolvers running 9.18.0 that have both dnssec-validation and synth-from-dnssec enabled. (Note that dnssec-validation auto; is the default setting unless configured otherwise in named.conf and that enabling dnssec-validation automatically enables synth-from-dnssec unless explicitly disabled) Versions affected: BIND 9.18.0
affected:
{
product: BIND
vendor: ISC
versions:
status: affected, version: Open Source Branch 9.18 9.18.0
}
metrics:
cvssV3_1: [
attackComplexity: LOW
attackVector: NETWORK
availabilityImpact: HIGH
baseScore: 7.5
baseSeverity: HIGH
confidentialityImpact: NONE
integrityImpact: NONE
privilegesRequired: NONE
scope: UNCHANGED
userInteraction: NONE
vectorString: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
version: 3.1
]
solutions:  Users of BIND 9.18.0 should upgrade to BIND 9.18.1
workarounds: The failure can be avoided by adding this option to named.conf:
synth-from-dnssec no;