The history of computers is full of underestimation: 640 kilobyte, 2-digit years, and 32-bit Internet addresses. IPv6 was invented to overcome the latter as well as to revise other drawbacks and security vulnerabilities of its predecessor IPv4. Initially considered the savior in terms of security because of its mandatory IPsec support, it turned out not to be the panacea it was thought to be. Outsourcing security to IPsec but eventually removing it as well as other design decisions led to a number of vulnerabilities. They range from the already known spoofing of answers to link-layer address requests to novel possibilities regarding node tracking. In an effort to fix them, a vast amount of updates have been introduced. In this paper, we discuss security and privacy vulnerabilities with regard to IPv6 and their current countermeasures. In a second step, vulnerabilities and countermeasures are systematized by the appliance of an extendible common language for computer security incidents. Our evaluation shows that a large part of vulnerabilities can be mitigated but several security challenges remain. We deduce three main research challenges for IPv6 security, namely address assignment and structure, securing local network discovery, and address selection for reconnaissance.