[userbinator]

Regular expressions in DNS records? That sounds like it would be an easy possibility of exponential resource consumption: http://en.wikipedia.org/wiki/ReDoS

After a quick Google, it turns out some versions of ISC BIND were vulnerable to this... but I'm almost willing to bet a lot of other software that handles NAPTR could be as well.

[sleepydog]

Hopefully they use re2[1] or a similar regexp engine without backtracking.

[1]: https://code.google.com/p/re2/