The VirtualBox Linux kernel driver (vboxdrv) is probably not loaded.You may not have kernel driver installed for kernel that is runnig, if so you may do as root:
$ yum install kmod-VirtualBox-$(uname -r) kmod-VirtualBox
On not stable versions of Fedora you need use akmods (because we don't have pre-built kmods) or for custom kernels, you may do instead as root:
$ yum install akmod-VirtualBox kernel-devel-$(uname -r); akmods
If you installed VirtualBox packages and don't had reboot the system, you may need load the kernel driver, doing as root:
$ systemctl restart systemd-modules-load.service
Finally, at ~/.bashrc
add:
# Virtual Box - Kernel
KERN_DIR=/usr/src/kernels/`uname -r`
export KERN_DIR