sudo apt-get update
sudo apt-get install linux-headers-$(uname -r)
# if any errors then open /etc/apt/sources.list and add the following
deb http://http.kali.org/ /kali main contrib non-free
deb http://http.kali.org/ /wheezy main contrib non-free
deb http://http.kali.org/kali kali-dev main contrib non-free
deb http://http.kali.org/kali kali-dev main/debian-installer
deb-src http://http.kali.org/kali kali-dev main contrib non-free
deb http://http.kali.org/kali kali main contrib non-free
deb http://http.kali.org/kali kali main/debian-installer
deb-src http://http.kali.org/kali kali main contrib non-free
deb http://security.kali.org/kali-security kali/updates main contrib non-free
deb-src http://security.kali.org/kali-security kali/updates main contrib non-free
deb http://repo.kali.org/kali kali-bleeding-edge main
# then run the first two commands again