As per upstream advisory:
In BIND Supported Preview Edition, an error in the nxdomain-redirect feature can occur in versions which support EDNS Client Subnet (ECS) features. In those versions which have ECS support, enabling nxdomain-redirect is likely to lead to BIND exiting due to assertion failure.
If nxdomain-redirect is enabled (via configuration) in a vulnerable BIND release, a malicious party can cause BIND to exit by deliberately triggering the bug.
This issue only affects the special feature preview branch of bind. Bind packages shipped with Red Hat Enterprise Linux are not affected by this flaw.