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Serious Bug in macOS will Crash after 49 days

boppin

boppin

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Hi,

No News at MacRumors?

Michael Tsai did also wrote something in his blog. Good man!

photon.codes

We Found a Ticking Time Bomb in macOS TCP Networking - It Detonates After Exactly 49 Days - Photon Blog

Every Mac has a hidden expiration date. After exactly 49 days, 17 hours, 2 minutes, and 47 seconds of continuous uptime, a 32-bit unsigned integer overflow in Apple's XNU kernel freezes the internal TCP timestamp clock. Once frozen, TIME_WAIT connections never expire, ephemeral ports slowly...
photon.codes photon.codes
 
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German commentora wrote:

I can observe this peculiar network behavior under Sequoia as well; after a restart, everything is fine again – so is this perhaps not just a problem since Tahoe, but also with Sequoia?

…so is this perhaps not just a problem since Tahoe, but also with Sequoia?

Michael Tsaj's blog stated yesterday that it might date back to Catalina.

My MacBook is usually always active and only goes into sleep mode; somehow I hadn't noticed this error before – currently running Sequoia 15.7.5.

That explains why the internet only worked again after a restart recently…

I think I misunderstood something. Hence the question: could the bug also be related to the regular and brief Ethernet outages? MacStudio repeatedly pauses for several dozen seconds, during which the Ethernet is simply deactivated. Tested: The Wi-Fi connection works, though.

I don't really use them, though, since the router and computer are less than two meters apart. The Ethernet dropouts are intermittent, and the computer is always switched off overnight. Since other users are also reporting Ethernet dropouts specifically with MacStudio, I'm wondering if there's a more fundamental problem that might be related to the one mentioned in the article, even though the problem descriptions are quite different.

www.mactechnews.de

Kurioser Fehler in Tahoe: Netzwerkversagen nach 50 Tagen

Ein Programmierfehler in macOS 26 führt dazu, dass 49,71 Tage nach Neustart überflüssige Netzwerkverbindungen nicht mehr gelöst werden. Kurz darauf zeigt ein betroffener Mac unerklärliche Verbindungsprobleme. Die Ursache verbirgt sich tief in macOS.
www.mactechnews.de www.mactechnews.de
 
dmr727 said:
I never shut down my MBA unless I do an OS update, and haven't noticed any internet issues. It's always been rock solid. This is with Sequoia.
Click to expand...
Did you actually read the article? It's about these devices running continuously, and after 49 days, no further network connections can be established. It's very reminiscent of the bug in Windows 98, where the device would simply freeze after exactly 49 days of continuous operation. This is especially annoying for people who only ever put their devices into sleep mode. That would also explain why my old Intel-based Macs weren't as fast after such a long period. Originally, I only ever put them to sleep and never shut them down.
 
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I have had the occasional uptime well beyond 50 days, beyond 60 days, and encountered no issues. That's on Sequoia with my M4 Mac and not using any sleep mode. Unfortunately I just rebooted for 15.7.5 a week ago so it will be more than a month until I can verify this bug on my Mac. I don't doubt that it exists and my Mac might have been affected without me noticing.

bogdanw said:
People that don't shut down their Macs for 49 days deserve to have them crashing 🙂
Click to expand...
That's of course nonsense. Modern Apple silicon Macs have an idle power draw of 2-3W and it simply isn't worth wasting time to set up my workspace from scratch with no benefit whatsoever. Wait until you find out how long servers and various computer and network appliances are kept up and running in between reboots. These vary from weeks and months to actual years and often have special engineering with redundant hardware that allows parts to fail and be replaced without a reboot and might run software that can be kept up-to-date without a reboot.

The last time I had to reboot a computer regularly was around 2020 with an Intel Macbook that would crash regularly. Then I switched to a M1 Mac in 2021 and haven't had a single crash or kernel panic since.
 
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okkibs said:
I have had the occasional uptime well beyond 50 days, beyond 60 days, and encountered no issues.
Click to expand...
I've had uptime of well over a year and haven't run into this issue.

dmr727 said:
The article didn't seem to indicate that sleep mode reset the 49 day clock.
Click to expand...
Ah, well that might explain it. It's a laptop so I put it to sleep daily.

Edit: Despite the original article claiming that MacOS 12 is affected, a later comment in this thread says that it's a new bug. That would explain why I haven't run into it: my Macs are on 12 and 15.
 
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When I ran OS/2, I would reboot the computer once a year, whether it needed it or not.

I reboot MacOS (and iOS) far more often: maybe once a month or so.
 
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okkibs said:
That's of course nonsense. Modern Apple silicon Macs have an idle power draw of 2-3W and it simply isn't worth wasting time to set up my workspace from scratch with no benefit whatsoever. Wait until you find out how long servers and various computer and network appliances are kept up and running in between reboots. These vary from weeks and months to actual years and often have special engineering with redundant hardware that allows parts to fail and be replaced without a reboot and might run software that can be kept up-to-date without a reboot.

The last time I had to reboot a computer regularly was around 2020 with an Intel Macbook that would crash regularly. Then I switched to a M1 Mac in 2021 and haven't had a single crash or kernel panic since.
Click to expand...
I was joking, as indicated by the smiley face at the end.

But if you want to talk seriously, may I remind you that current Macs are consumer devices, not servers. Apple has discontinued Xserve in 2011 and Mac OS X Server in 2022. macOS performs important maintenance tasks at shutdown/startup. I’ll mention just cleaning /tmp.

If you follow Apple’s advice at keeping your Mac updated, you have to restart on average about once every month. (macOS Tahoe 26 15 Sep 2025 - macOS Tahoe 26.4.1 09 Apr 2026).
https://support.apple.com/en-us/100100

To avoid confusions, this is a joke: for those who don’t know how to shut down their Macs, Apple has a support page “Shut down or restart your Mac” https://support.apple.com/en-kz/guide/mac-help/mchlp2522/mac
 
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okkibs said:
Wait until you find out how long servers and various computer and network appliances are kept up and running in between reboots. These vary from weeks and months to actual years and often have special engineering with redundant hardware that allows parts to fail and be replaced without a reboot and might run software that can be kept up-to-date without a reboot.
Click to expand...
On one hand, that's a very good point. A data center with tens of thousands of servers can't be rebooting them regularly.

On the other hand,Apple does not use any version of MacOS in its data center servers (other than a testing cloud for app developers).
 
German Mac magazine MacWelt wrote an article:

Bug in macOS 26 Tahoe: Servers crash after 49 days

The bug is caused by the peculiarity of the number system in Unix. It affects users who use Macs as servers.

www.macwelt.de

Bug in macOS 26 Tahoe: Server stürzen nach 49 Tagen ab

Der Bug ist durch die Besonderheit des Zahlensystems in Unix verursacht. Betroffen sind Nutzer, die Macs als Server verwenden.
www.macwelt.de www.macwelt.de

Honestly, I'm surprised such a bug even occurs. After all, Apple markets its macOS as UNIX, and I would expect better behavior from the operating system.

Shut down or restart will reset the timer.
 
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