Package: pdns-server Version: 3.4.1-4+deb8u5 I used apt-get to upgrade from version 3.4.1-4+deb8u4 to 3.4.1-4+deb8u5 which left me with 100% Powerdns CPU usage (before the upgrade it was in the 25-30% range) and a mostly unresponsive Powerdns server. There are no messages in the error logs. Aside from the Powerdns upgrade and a bunch of upgrades for other packages, apt-get also installed an upgrade for Libbotan (from 1.10.8-2 to 1.10.8-2+deb8u1) and after some testing the combination of the Powerdns and Libbotan packages turned out to be the source of the problem: when I downgraded both packages back to 3.4.1-4+deb8u4 and 1.10.8-2 respectively, everything was fine again.
It's a plain Debian installation (Jessie) that we keep up-to-date using apt-get. We use the Powerdns Mysql backend.