Samba from version 4.9.0 and before version 4.9.3 is vulnerable to a NULL pointer de-reference. During the processing of an DNS zone in the DNS management DCE/RPC server, the internal DNS server or the Samba DLZ plugin for BIND9, if the DSPROPERTY_ZONE_MASTER_SERVERS property or DSPROPERTY_ZONE_SCAVENGING_SERVERS property is set, the server will follow a NULL pointer and terminate. There is no further vulnerability associated with this issue, merely a denial of service.