SmartDNS through 41 before 56d0332 allows an out-of-bounds write because of a stack-based buffer overflow in the _dns_encode_domain function in the dns.c file, via a crafted DNS request.
https://github.com/pymumu/smartdns/issues/1378
https://github.com/pymumu/smartdns/commit/56d0332bf91104cfc877635f6c82e9348587df04