49‑day macOS networking bug
Researchers uncovered a macOS bug that appears after roughly 49.7 days of uptime, freezing the system’s internal network clock and causing apps and websites to stop working. While not an official Apple disclosure, the report highlights a class of long‑uptime failures that often show up in labs and CI systems rather than consumer testing. Such soak-test edge cases can quietly degrade automation reliability and test throughput in manufacturing environments. (digitaltrends.com)
A Mac can sit there looking fine for 49 days, 17 hours, 2 minutes, and 47 seconds, and then suddenly stop opening new websites and apps that need the internet. The trigger is not Wi‑Fi hardware or your router; Photon traced it to a timer inside Apple’s XNU kernel, which is the low-level code that runs macOS. (photon.codes) That timer is a 32-bit counter, which is just a box for numbers that tops out at 4,294,967,295. If you count milliseconds in that box, you hit the ceiling at about 49.7 days, and the number wraps back to zero like a car odometer rolling over. (photon.codes) The part of macOS that breaks is Transmission Control Protocol timing. Transmission Control Protocol is the rulebook that lets your Mac open and close reliable internet conversations, like loading a web page or signing into an app. (photon.codes) When one of those conversations ends, macOS does not throw it away immediately. It parks the connection in a holding area called TIME_WAIT for 30 seconds on macOS, the same way a theater keeps an aisle clear for a moment after a crowd leaves. (photon.codes) That 30-second cleanup depends on the internal clock still moving forward. After the 49.7-day rollover, Photon says the clock freezes, TIME_WAIT entries never expire, and the system slowly runs out of ephemeral ports, which are the temporary numbered slots a computer uses for new outgoing connections. (photon.codes) The weird part is that the failure is partial, not total. Photon and follow-up coverage say Internet Control Message Protocol ping can still work, and connections that were already open before the rollover can keep going, while only new Transmission Control Protocol connections fail. (photon.codes) (digitaltrends.com) That is why this bug hides so well in real life. A browser tab you opened earlier may still stream audio, while a fresh login window, a software update check, or a new web request quietly stalls and makes the Mac look randomly broken. (digitaltrends.com) Most home users may never notice because security updates and normal restarts usually happen before 49 days of uptime. TidBITS notes that sleep can stretch the timeline further, and it says the bug appears to be tied to macOS 26 rather than older releases. (tidbits.com) The people who do get hit are the ones who leave Macs running on purpose. Photon found the issue on its iMessage monitoring fleet, and the same kind of long-uptime pattern shows up in build machines, lab rigs, and factory automation systems that are expected to stay on for weeks at a time. (photon.codes) (digitaltrends.com) There is no Apple fix publicly documented yet as of April 10, 2026. The practical workaround today is simple: reboot the Mac before it crosses 49 days of uptime, which resets the counter and clears the stuck connection state. (tidbits.com) (digitaltrends.com)
