title: named configured to answer from stale cache may terminate unexpectedly while processing RRSIG queries
description: BIND 9 resolver can crash when stale cache and stale answers are enabled, option `stale-answer-client-timeout` is set to a positive integer, and the resolver receives an RRSIG query.
This issue affects BIND 9 versions 9.16.12 through 9.16.36, 9.18.0 through 9.18.10, 9.19.0 through 9.19.8, and 9.16.12-S1 through 9.16.36-S1.
affected:
{
vendor: ISC
product: BIND 9
versions:
version: 9.16.12, lessThanOrEqual: 9.16.36, status: affected, versionType: custom
version: 9.18.0, lessThanOrEqual: 9.18.10, status: affected, versionType: custom
version: 9.19.0, lessThanOrEqual: 9.19.8, status: affected, versionType: custom
version: 9.16.12-S1, lessThanOrEqual: 9.16.36-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: 9.16.37, 9.18.11, 9.19.9, or 9.16.37-S1.
workarounds: Setting `stale-answer-client-timeout` to `0` or to `off/disabled` will prevent BIND from crashing due to this issue.