OpenVPN 2.x on Windows created the --service exit event and the netsh.exe guard semaphore with a NULL DACL, which allows a local user to interfere with other users' openvpn processes by blocking the netsh semaphore or by signalling the exit event, leading to a local denial of service. Only setups not using the interactive service, or using the automatic service to start and stop openvpn, are affected. OpenVPN version 2.0.0 through 2.6.22 and 2.7_alpha1 through 2.7.6 are affected. This is fixed in version 2.7.7.