syzkaller is an unsupervised coverage-guided kernel fuzzer. Supports FreeBSD, Fuchsia, gVisor, Linux, NetBSD, OpenBSD, and Windows. Initially, syzkaller was developed with Linux kernel fuzzing in mind, but now it's being extended to support other OS kernels as well. Once syzkaller detects a kernel crash in one of the VMs, it will automatically start the process of reproducing this crash. By default, it will use 4 VMs to reproduce the crash and then minimize the program that caused it. This may stop the fuzzing, since all of the VMs might be busy reproducing detected crashes. The process of reproducing one crash may take from a few minutes up to an hour depending on whether the crash is easily reproducible or non-reproducible at all.