CVE 2017-15120
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.
See the 
CVE page on Mitre.org
for more details.
