.NET 8 and .NET 9 Lose Microsoft Support on November 10

Six days from now, Microsoft stops sending security fixes for two versions of .NET that millions of production apps still run on. If your company built anything on .NET 8 or .NET 9 in the last couple of years, this is the week to check which one.

What's actually ending

Microsoft's own .NET blog confirms it plainly: both .NET 8 and .NET 9 reach end of support on November 10, 2026. After that date, there are no more servicing updates, no more security patches, and no more technical support for either runtime, regardless of how widely they're still deployed.

That might sound odd, since .NET 8 and .NET 9 came out more than a year apart and were meant to be supported on different schedules — .NET 8 as a Long-Term Support (LTS) release good for three years, .NET 9 as a Short-Term Support (STS) release good for only 18 months. Microsoft later stretched STS support from 18 to 24 months, which pushed .NET 9's cutoff forward and landed it on the exact same date as .NET 8's original LTS expiry. Two releases, two different lifecycles, one shared deadline.

Apps built on either version won't suddenly stop working on November 11. They'll keep running exactly as before. What changes is that any new vulnerability discovered in the runtime from that point on simply won't get fixed — not for a known critical bug, not for anything. Microsoft's replacement is .NET 10, an LTS release supported through November 2028, and it's already been out long enough that most teams have had a real window to test on it.

Why this lands harder in India than most places

This isn't an abstract lifecycle footnote for Indian developers. India is one of the largest hubs of enterprise .NET development anywhere, largely because of how deeply IT services majors and their banking, insurance, and retail clients lean on the Microsoft stack. A huge share of that work is maintenance and support contracts for applications built years ago and rarely touched since — exactly the kind of codebase most likely to still be sitting on .NET 8 or .NET 9 with nobody tracking the support calendar.

Running an unsupported runtime isn't just a compliance checkbox either. For companies handling financial or personal data, it collides directly with how India's Digital Personal Data Protection (DPDP) Act expects "reasonable security safeguards" to be maintained — a requirement that gets much harder to defend once your core runtime stops receiving security fixes by design. Auditors and clients abroad increasingly ask about this directly during vendor reviews, and "still on an end-of-life runtime" is not an answer that lands well.

"After November 10, 2026, Microsoft will no longer provide servicing updates, security fixes, or technical support for .NET 8 or .NET 9." — Microsoft, .NET Blog

For teams deciding what to do this week, the practical path looks roughly like this:

• Check which .NET version every production service actually runs — not what the repo says, what's deployed.
• If you're on .NET 9, moving to .NET 10 is usually a smaller jump than it looks, since it's the very next version.
• If you're on .NET 8, budget real time — LTS-to-LTS upgrades across a large codebase can surface breaking changes in dependencies, not just the runtime itself.
• Watch for Visual Studio 2022 flagging .NET 8 and .NET 9 components as out of support in an upcoming servicing update — that's often the first internal alarm bell teams notice.

None of this is unique to Microsoft's ecosystem — Node, Python, and Java all run similar support clocks, and plenty of production systems everywhere quietly outlive their vendor's patch commitments. But .NET's support model is unusually precise about dates, which is exactly why there's no excuse for this one to sneak up on anybody. The calendar's been public for months; the only question now is whether the upgrade got scheduled or got postponed until it became an incident.