I was unable to install Guest Additions on previous VirtualBox 4.3.16 on my CentOS 7. But now after I update my VirtualBox installation to version 4.3.18, the guest additions installed successfully without problems. If you facing the same problems with me, try to upgrade your VirtualBox to version 4.3.18 and reinstall the guest additions.
Steps to install Guest Additions on CentOS 7
A. Install required packages and tools
Execute the following commands on Terminal to install additional packages needed for the guest additions installation
yum groupinstall "Development Tools"
yum install kernel-devel
Now reboot CentOS 7
B. Install Guest Additions
Go to Devices | Install Guest Additions CD Image from your VirtualBox window. Then the CD image should be mounted automatically in CentOS virtual machine. Simply press Run and enter your root password
Or, we need to run it manually. Open Files and click the Guest Additions
Now click Run Software. Enter your root password and the installation will begin after that. Should be there are no errors and reboot your virtual machine when finished. After reboot, enjoy CentOS 7 with full features unlocked on VirtualBox. Enjoy.