title: BIND Supported Preview Edition can exit with an assertion failure if ECS is in use
description: An error in the EDNS Client Subnet (ECS) feature for recursive resolvers can cause BIND to exit with an assertion failure when processing a response that has malformed RRSIGs. Versions affected: BIND 9.10.5-S1 -> 9.11.6-S1 of BIND 9 Supported Preview Edition.
problem types: An attacker who is able to cause a server to perform a query whose answer will be accompanied by malformed RRSIGs can deliberately cause a server to exit if it is using the recursive ECS feature.
affected:
{
product: BIND 9 Supported Preview Edition
vendor: ISC
versions:
status: affected, version: BIND 9.10.5-S1 -> 9.11.6-S1 of BIND 9 Supported Preview Edition.
}
metrics:
cvssV3_0: [
attackComplexity: HIGH
attackVector: NETWORK
availabilityImpact: HIGH
baseScore: 5.9
baseSeverity: MEDIUM
confidentialityImpact: NONE
integrityImpact: NONE
privilegesRequired: NONE
scope: UNCHANGED
userInteraction: NONE
vectorString: CVSS:3.0/AV:N/AC:H/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:
BIND Supported Preview Edition is a special feature preview branch of BIND provided to eligible ISC support customers.
>=    BIND 9.11.7-S1
workarounds: Only servers which have enabled the EDNS Client Subnet (ECS) feature can be affected by this defect; it can be prevented by disabling ECS options in the server's configuration.