This document is about PowerDNS 4.X. If you have PowerDNS 3.X, please see the PowerDNS 3.X documentation

PowerDNS Security Advisory 2006-02: Zero second CNAME TTLs can make PowerDNS exhaust allocated stack space, and crash

PowerDNS would recurse endlessly on encountering a CNAME loop consisting entirely of zero second CNAME records, eventually exceeding resources and crashing.