These instructions are outdated because only macOS 10.15.0 is affected. Install macOS 10.15.1 or later to fix the issue descibed here.
When you install Little Snitch on the initial version of macOS Catalina (version 10.15.0), you may get an error message “Little Snitch version mismatch detected” after restarting your Mac. This is due to a bug in macOS Catalina 10.15.0. The operating system sometimes fails to successfully complete the necessary boot cache update for the newly installed kernel extension. Unfortunately it’s not possible to fix this problem in the Little Snitch Installer. It requires a fix in macOS, and Apple fixed this in macOS 10.15.1.
Our original workaround consisted of these steps:
Restart your system in macOS Recovery. Learn more
If you have enabled FileVault to encrypt the contents of your system volume, you first have to mount that volume: Open “Disk Utility”, select your system volume in the sidebar and click the “Mount” button in the toolbar. Please be patient – mounting FileVault volumes may take quite a while. Once the volume is mounted, quit the “Disk Utility” application.
Open “Terminal” from the Utilities menu in the menu bar.
Enter the following command:
touch -c "/Volumes/Macintosh HD/System/Library/Extensions"
Important Note: If your system volume has a different name than “Macintosh HD”, replace this name with the actual name of the volume on which macOS Catalina is installed. Note that “macOS Base System” is not the volume you’re looking for (that’s the name of the volume for Recovery Mode).
- Wait about 10 seconds. Then choose “Restart” from the Apple menu in the menu bar to restart your computer. Shutting down can take up to a few minutes because the system is rebuilding the boot cache in the background. Note that during this time no progress indication is shown.