While this has nothing to do specifically with the topic of DNSSEC that we cover here on Deploy360, there is important news in the broader world of “DNS security”. The vendors of three of the major DNS recursive resolvers today released security advisories about a particularly nasty bug where the resolver can be tricked into trying to follow essentially an infinite loop and wind up exhausting all resources and potentially shutting down. The advisories from BIND, PowerDNS and Unbound are found at these links:
- BIND: CVE-2014-8500: A Defect in Delegation Handling Can Be Exploited to Crash BIND
- PowerDNS: Security Advisory 2014-02: PowerDNS Recursor 3.6.1 and earlier can be made to provide bad service
- Unbound: Unbound security advisory
The advisories from both PowerDNS and Unbound indicate that this bug would be difficult for an attacker to exploit unless they were within the user base of the recursive resolver. The BIND advisory is more open-ended and indicates the bug could be executed remotely.
In all cases the easiest solution is to upgrade to the newest versions:
While there are apparently no known exploits of the bug in the wild yet, that will now only be a matter of time. It would be best to upgrade your recursive resolvers as soon as possible.
P.S. While you are in there updating your DNS resolver, if you are using BIND or Unbound, why not enable DNSSEC validation? It’s a simple change in the configuration file, as shown in this SURFnet white paper.