An issue has been found in the parsing of authoritative answers in PowerDNS Recursor before 4.0.8, leading to a NULL pointer dereference when parsing a specially crafted answer containing a CNAME of a different class than IN. An unauthenticated remote attacker could cause a denial of service.
https://www.debian.org/security/2017/dsa-4063
https://doc.powerdns.com/recursor/security-advisories/powerdns-advisory-2017-08.html
https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2017-15120