The c-ares function aresparsenaptrreply(), which is used for parsing NAPTR responses, could be triggered to read memory outside of the given input buffer if the passed in DNS response packet was crafted in a particular way.

A security vulnerability has been discovered in the c-ares library that is bundled with all versions of Node.js. Due to the difficulty of triggering and making use of this vulnerability we currently consider this a low-severity security flaw for Node.js users.

More information at https://c-ares.haxx.se/adv20160929.html