&gt;If you had the same version of OpenSMTPD running on a generic Linux kernel or on Mac OS X, it was vulnerable<p>You&#x27;re completely wrong, stack canaries have nothing to do with kernels, they&#x27;re a compiler option, gcc has them enabled by default, clang has them enabled by default. So no, running OpenSMTPD on Linux or OS X would not make that vulnerability exploitable.