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Parallels Desktop system extensions are blocked on macOS 10.13 High Sierra

APPLIES TO:
  • Parallels Desktop for Mac Business Edition
  • Parallels Desktop for Mac Home Edition
  • Parallels Desktop for Mac Pro Edition

Symptoms

  • When I start Parallels Desktop for Mac on macOS High Sierra I get the following warning:

    System Extension Blocked. A program tried to load a new system extension signed by "Parallels International GmbH" and it was blocked. If you want to enable extensions from this developer, go to the Security & Privacy System Preferences pane.

Cause

macOS High Sierra 10.13 introduces a new feature that requires user approval before loading newly-installed third-party kernel extensions. Third-party kernel extensions (KEXTs) that were already present when upgrading to macOS High Sierra are granted automatic approval.

This approval UI is only present in the Security & Privacy preferences pane for 30 minutes after the alert. Until the user approves the KEXT, future load attempts will cause the approval UI to reappear but will not trigger another user alert.

For more information please refer to the Apple's official tech note: Technical Note TN2459.

Moreover, it's not possible to press Allow button if a connection to Mac established remotely due to security-related configuration of macOS to block any security related actions for remote connections.

Resolution

Open System Preferences > Security & Privacy > General > click Allow next to the corresponding message:

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If it's not possible to click Allow button or after clicking it nothing happens, ensure that the following recommendations are followed:

  1. Allow button is pressed locally. As mentioned above, due to macOS security limitations it's not possible to press Allow button (nothing will happen as a result of pressing it) remotely (any source of remote connection).
  2. No third-party input methods (keyboards, mouses, touch pads, graphics tablets) and their software are present at the moment Allow button is pressed.
    Presence of third-party input methods and their software/drivers could possible cause the inability to press Allow button. Temporarily disconnect such devices from the Mac and remove their software/drivers.
    It has been proven that only a presence of MagicPrefs preference pane render the Allow button unusable. Once Allow button is successfully used, macOS will store this record and it would be possible to continue using previously disconnected devices and install their software/drivers back.

Advanced solution

If pressing Allow button using the mouse doesn't give any positive results, use the steps described below:

  1. Open System Preferences > Security & Privacy > Keyboard > Shortcuts and switch Full Keyboard Access to All controls.
  2. Now open System Preferences > Security & Privacy > General.
  3. Press Tab key on the keyboard until the Allow button is highlighted, then hit Spacebar on the keyboard to press Allow button.
  4. Close System Preferences window and start Parallels Desktop.

Why Parallels Desktop needs its own kernel extensions?

To deliver all Parallels Desktop features, such as virtualization, USB and Network, Parallels Desktop loads the following kernel extensions to macOS:

com.parallels.kext.hypervisor - a proprietary core virtualization driver, which makes Parallels Desktop the best virtualization solution for Mac.

com.parallels.kext.vnic - Shared Network driver, which is used by a virtual router who manages all network services for a VM, such as gateway,DNS, DHCP, port forwarding, network conditioner etc.

com.parallels.kext.usbconnect - USB driver, loaded when a USB device connects to a virtual machine (VM). Supports all USB data transfer protocols except of isochronous transfer.

com.parallels.kext.netbridge - Bridged Network driver, creates a virtual network adapter on Mac to connect a VM to Mac's subnet directly.




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