title: Malformed NSEC records can cause named to terminate unexpectedly when synth-from-dnssec is enabled
description: A `named` instance configured to run as a DNSSEC-validating recursive resolver with the Aggressive Use of DNSSEC-Validated Cache (RFC 8198) option (`synth-from-dnssec`) enabled can be remotely terminated using a zone with a malformed NSEC record.
This issue affects BIND 9 versions 9.16.8-S1 through 9.16.41-S1 and 9.18.11-S1 through 9.18.15-S1.
affected:
{
vendor: ISC
product: BIND 9
versions:
version: 9.16.8-S1, lessThanOrEqual: 9.16.41-S1, status: affected, versionType: custom
version: 9.18.11-S1, lessThanOrEqual: 9.18.15-S1, status: affected, versionType: custom
defaultStatus: unaffected
}
metrics:
cvssV3_1: [
version: 3.1
attackVector: NETWORK
attackComplexity: LOW
privilegesRequired: NONE
userInteraction: NONE
scope: UNCHANGED
confidentialityImpact: NONE
integrityImpact: NONE
availabilityImpact: HIGH
vectorString: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
baseScore: 7.5
baseSeverity: HIGH
]
exploits: We are not aware of any active exploits.
solutions: Upgrade to the patched release most closely related to your current version of BIND 9: 9.16.42-S1 or 9.18.16-S1.
workarounds: Setting `synth-from-dnssec` to `no` prevents the problem.