Linux has been the first to offer a complete implementation of RFC5961 in its TCP/IP stack, designed to prevent certain kinds of hacking attacks. Now it turns out there’s a flaw in the spec itself, which creates its own vulnerability <http://arstechnica.com/security/2016/08/linux-bug-leaves-usa-today-other-top-sites-vulnerable-to-serious-hijacking-attacks/>: The problematic RFC 5961 has not yet been fully implemented in Windows or Mac OS X, so those operating systems aren't believed to be vulnerable. By contrast, the Linux operating system kernel, starting with version 3.6 introduced in 2012, has added a largely complete set of functions implementing the standard. Linux kernel maintainers released a fix with version 4.7 almost three weeks ago, but the patch has not yet been applied to most mainstream distributions.