Ray Morris discovered that the PowerDNS authoritative server responds to response packets. An attacker who can spoof the source address of IP packets can cause an endless packet loop between a PowerDNS authoritative server and another DNS server, leading to a denial of service.
For the oldstable distribution (lenny), this problem has been fixed in version 184.108.40.206-1+lenny1.
For the stable distribution (squeeze), this problem has been fixed in version 2.9.22-8+squeeze1.
For the testing distribution (wheezy) and the unstable distribution (sid), this problem will be fixed soon.
We recommend that you upgrade your pdns packages.