NordVPN for Windows allows local attackers to stop unprotected Windows system services and change their startup type to Manual via named pipes. The NordVPN user-mode application allows a low-privileged attacker to act as a trusted process and connect to the named pipe "\.\pipe\nord-security\v1\NordVpnService\Server". The attacker can then invoke the "ISettingsGrpc.StopService" and "ISettingsGrpc.ChangeServiceStartType" methods with an arbitrary service name, allowing them to stop any unprotected Windows service and change its startup type. This leads to denial of service of critical system services. Services protected by Windows (PPL processes, Windows Tamper Protection), such as Windows Defender, cannot be stopped or reconfigured.
This issue was fixed in version 8.12