macOS has a 49.7-day networking time bomb built in that only a reboot fixes

Researchers at Photon found a macOS bug that causes the TCP stack to stop creating new connections after about 49.7 days of uptime.

The issue is caused by tcp_now, a 32-bit millisecond counter that wraps after 4,294,967,295 and is mishandled by Apple's XNU kernel.

When tcp_now hits its limit, connection expiration math overflows, preventing closed connections from being removed and exhausting ephemeral ports.

Photon says rebooting affected Macs clears the fault and the team is developing an alternative mitigation.