Apple MacBooks slow down after 49 days due to "macOS time bomb"

If you own a MacBook Neo ($599 on Amazon), a MacBook Pro or even an iMac and rarely restart this computer, you will often notice the device slows down after a few weeks while some apps no longer work as expected. Photon has now identified a bug that effectively acts like a time bomb and is likely to be responsible for some of these problems.

This bug means that after exactly 49 days, 17 hours, 2 minutes and 47.296 seconds from the moment a Mac is switched on, network connections are no longer terminated correctly. This initially leads to an increase in CPU utilization, because after some time hundreds or even thousands of connections are managed that should actually have been terminated. As soon as the available ports, usually 16,384 in number, are used up, no more new connections can be established.

From this point on, many applications no longer work properly, although network connections that were previously established continue to work without any problems and macOS also responds correctly to a ping. A restart resets this countdown and thus fixes the problem for exactly 49 days until it occurs again. This period is no coincidence, as macOS uses a 32-bit counter to determine the time and duration of network connections.

It can therefore store values up to 2³², which corresponds to 4,294,967,295 nanoseconds or 49 days, 17 hours, 2 minutes and 47.296 seconds. If this value is exceeded, the counter overflows and stops working. For the same reason, Windows 95 and Windows 98 crashed after 49.7 days, while some Linux derivatives record the seconds since January 1, 1970 with a 32-bit counter, which can lead to errors on January 19, 2038. More information on the background to this error can be found in the informative report from Photon.