CVE 2015-1868
The label decompression functionality in PowerDNS Recursor 3.5.x, 3.6.x before 3.6.3, and 3.7.x before 3.7.2 and Authoritative (Auth) Server 3.2.x, 3.3.x before 3.3.2, and 3.4.x before 3.4.4 allows remote attackers to cause a denial of service (CPU consumption or crash) via a request with a name that refers to itself.
See the 
CVE page on Mitre.org
for more details.
