title: named may terminate unexpectedly under high DNS-over-TLS query load
description: A flaw in the networking code handling DNS-over-TLS queries may cause `named` to terminate unexpectedly due to an assertion failure. This happens when internal data structures are incorrectly reused under significant DNS-over-TLS query load.
This issue affects BIND 9 versions 9.18.0 through 9.18.18 and 9.18.11-S1 through 9.18.18-S1.
affected:
{
vendor: ISC
product: BIND 9
versions:
version: 9.18.0, lessThanOrEqual: 9.18.18, status: affected, versionType: custom
version: 9.18.11-S1, lessThanOrEqual: 9.18.18-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: 9.18.19 or 9.18.19-S1.
workarounds: Disabling listening for DNS-over-TLS connections (by removing `listen-on ... tls ... { ... };` statements from the configuration) prevents the affected code paths from being taken, rendering exploitation impossible. However, there is no workaround for this flaw if DNS-over-TLS support is required.