A memory leak in Apple’s Network Extension framework
Unfortunately that’s another new bug in the Network Extension framework of macOS. It’s a memory leak in Apple’s framework, which developers must use to create a firewall for the Mac. This bug first occurred in macOS 15.0 Sequoia.
On macOS 14 Sonoma you may get a hand full of leaks with a total of a few Kilobytes. That’s OK (sort of). But on macOS 15 Sequoia this can easily grow to hundreds of Megabytes and more.
This bug has already been reported to Apple (FB15552991), but if you are affected by this bug, feel free to send another report via Feedback Assistant (mentioning the existing report FB15552991). This might help Apple to find the cause of the issue and it increases the chance that Apple will prioritize the fix.
For the time being, if you encounter an unreasonably huge memory consumption, you may enforce a restart of the Network Extension. To do so, open the Activity Monitor app in Applications > Utilities, search for the at.obdev.littlesnitch.networkextension process (make sure that All Processes is selected in the View menu) and click the Stop button in the toolbar to quit the process. The extension will then restart automatically.
