Samba 4.9.x before 4.9.9 and 4.10.x before 4.10.5 has a NULL pointer dereference, leading to Denial of Service. This is related to the AD DC DNS management server (dnsserver) RPC server process.
https://www.synology.com/security/advisory/Synology_SA_19_27
https://www.samba.org/samba/security/CVE-2019-12435.html
https://usn.ubuntu.com/4018-1/
http://www.securityfocus.com/bid/108825
http://lists.opensuse.org/opensuse-security-announce/2019-07/msg00023.html