.NET 9 end of life
.NET 9 reaches end of support on 10 November 2026, the same day as .NET 8. It is a Standard Term Support release, and Microsoft's release notes list it as supported for two years from 12 November 2024. The latest build is 9.0.20, shipped on 8 September 2026. .NET 10 is the LTS target, supported to 14 November 2028. OSSeva ships patched .NET 9 runtimes after the date.
- End of life
- 10 November 2026
- Released
- Nov 2024
- Final release
- 9.0.20 (latest, 8 September 2026)
- Successor
- .NET 10 (LTS, supported to 14 November 2028)
Date published by Microsoft .NET release metadata. We do not publish a lifecycle date we cannot source.
Last reviewed
What actually stops on 10 November 2026
- Monthly servicing for the .NET 9 runtime, ASP.NET Core 9 and the 9.0 SDKs. Microsoft's metadata marks 9.0 as in maintenance with an end-of-life date of 10 November 2026.
- Security fixes. Microsoft has kept fixing .NET 9 into its last months: 9.0.20 alone closed six CVEs in September 2026, and advisories found after 10 November will not reach 9.0.
- Microsoft support cases for applications on .NET 9, and rebuilt .NET 9 container images with OS-level fixes.
What actually breaks in the upgrade
9 and 8 end together
.NET 8 and .NET 9 both reach end of support on 10 November 2026. A team that moved from 8 to 9 to buy time has no time left from that move, and a team on 9 cannot step back to 8. .NET 10, supported to 14 November 2028, is the only supported target.
One major, not two
From .NET 9 the move to .NET 10 is a single major version, so the breaking-change review covers one release instead of the two an 8 estate faces. Retarget from net9.0 to net10.0, update the NuGet packages that pinned 9.x versions, and rerun the test suite.
Self-contained apps each need a rebuild
Framework-dependent apps pick up whatever runtime the host has installed. Self-contained and single-file deployments carry their own runtime, so every one has to be rebuilt and redeployed to leave 9.0. Count them before you plan the dates.
Your options, costed honestly
Including the ones that do not involve buying anything from us.
| Option | What it is | Effort | Cost | Our view |
|---|---|---|---|---|
| Upgrade to .NET 10 | Retarget, update dependencies, retest, redeploy. | Days to weeks | Engineering time | The destination. One major version from 9, supported to November 2028. |
| OSSeva patched .NET 9 | Signed .NET 9 runtimes with backported security fixes after 10 November 2026. | Days | Subscription | For applications that cannot be retargeted and redeployed before the date. |
| Wait for .NET 11 | .NET 11 is at release candidate stage and is a Standard Term Support release. | Weeks | Engineering time | Does not solve 10 November. It is another short-support release. |
| Stay unpatched | No Microsoft fixes after 10 November 2026. | None | Zero now | Hard to defend for anything that faces the internet. ASP.NET Core has had critical advisories, such as CVE-2025-55315. |
What OSSeva does for .NET 9
OSSeva patches this line
OSSeva ships patched .NET 9 runtimes now, with security fixes backported to the runtime and ASP.NET Core 9 after Microsoft's last release. They are delivered as signed packages and container images through your own repository manager, on the Patch, Assure and Operate tiers.
.NET extended supportWhat your auditor will say
Every system component in the cardholder data environment needs its applicable security patches. A runtime, framework or broker with no upstream fix supply needs a patched source or a documented compensating control.
Auditors ask for evidence that production systems receive security fixes. A version past end of life fails that test unless another supplier ships the fixes and can show which CVEs they close.
.NET 9: common questions
When does .NET 9 reach end of support?
On 10 November 2026. Microsoft's release metadata lists 10 November 2026 as the end-of-life date for .NET 9, the same date as .NET 8.
Is .NET 9 an LTS release?
No. .NET 9 is a Standard Term Support release. Microsoft's .NET 9 release notes list it as supported for two years, from 12 November 2024 to 10 November 2026. .NET 8 and .NET 10 are the LTS releases around it.
Should I upgrade from .NET 9 to .NET 10?
Yes. .NET 10 is the LTS release and is supported to 14 November 2028. .NET 11 is a Standard Term Support release, so it gives a shorter window than .NET 10.
What was the last .NET 9 release?
The latest is 9.0.20, released on 8 September 2026 with runtime 9.0.20 and SDK 9.0.318. Microsoft ships .NET 9 servicing releases monthly until the end-of-support date.
Can I get security patches for .NET 9 after November 2026?
Not from Microsoft. OSSeva ships patched .NET 9 runtimes on the Patch, Assure and Operate tiers.
Still running .NET 9?
Tell us the versions and the estate size. We will tell you honestly whether to upgrade or to buy cover — and we say 'upgrade' more often than you would expect.