The error code KB4340558 arises on your system with an alert message “Access Denied.” It’s a buggy update error that most of the users are facing this annoying error. Sometimes, this error message appears on your system just after downloading Quality and Security rollup upgrades related to “.NET.” This error appears on your device if the .NET related programs and apps fails to run on your system. It might occur due to execution issue or restricted software permissions. “.NET” enables the particular program to execute and perform on your device, but the problem arises when the inspection permissions of your device fail to proceed.