title:  Assertion failure on delayed DS lookup
description: When the vulnerability is triggered the BIND process will exit. BIND 9.18.0
problem types: In BIND 9.18.0 the recursive client code was refactored. This refactoring introduced a "backstop lifetime timer".  While BIND is processing a request for a DS record that needs to be forwarded, it waits until this processing is complete or until the backstop lifetime timer has timed out. When the resume_dslookup() function is called as a result of such a timeout, the function does not test whether the fetch has previously been shut down. This introduces the possibility of triggering an assertion failure, which could cause the BIND process to terminate.  Only the BIND 9.18 branch is affected. BIND 9.18.0
affected:
{
platforms: all
product: BIND
vendor: ISC
versions:
status: affected, version: 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: No workarounds known.