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3874cae
publish 9B release notes
TaraOverfield Sep 4, 2026
5e0e0f7
Update release notes for September 2026 update
TaraOverfield Sep 5, 2026
566dcc6
Fix formatting of CVE-2026-62886 description
TaraOverfield Sep 5, 2026
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85 changes: 85 additions & 0 deletions docs/framework/release-notes/2026/09-08-september-cumulative-update.md
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---
title: September 2026 cumulative update
description: Learn about the improvements in the .NET Framework September 2026 cumulative update.
ms.date: 09/08/2026
ai-usage: ai-generated
---
# .NET Framework September 2026 cumulative update

_Released September 8, 2026_

## Summary of what's new in this release

- [Security improvements](#security-improvements)
- [Quality and reliability improvements](#quality-and-reliability-improvements)

### Security improvements

#### CVE-2026-62886 – Elevation of Privilege vulnerability

This security update addresses an elevation of privilege vulnerability detailed in [CVE-2026-62886](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-62886).

#### CVE-2026-69522 – Remote Code Execution vulnerability

This security update addresses a remote code execution vulnerability detailed in [CVE-2026-69522.](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-69522)

### Quality and reliability improvements

There are no new quality and reliability improvements in this release.
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## Known issues in this release

Microsoft is not currently aware of any issues in this update.

## Summary tables

The following table outlines the updates in this release.

| Product version | Cumulative update |
| --- | --- |
| **Windows 11, version 26H1** | |
| .NET Framework 4.8.1 | [5126053](https://support.microsoft.com/kb/5126053) |

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| **Windows 11, version 25H2** | |
| .NET Framework 3.5, 4.8.1 | [5126052](https://support.microsoft.com/kb/5126052) |

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| **Windows 11, version 24H2** | |
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| .NET Framework 3.5, 4.8.1 | [5126052](https://support.microsoft.com/kb/5126052) |

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| **Windows 11, version 23H2** | |
| .NET Framework 3.5, 4.8.1 | [5126424](https://support.microsoft.com/kb/5126424) |

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| **Windows Server 2025** | |
| .NET Framework 3.5, 4.8.1 | [5126052](https://support.microsoft.com/kb/5126052) |

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| **Windows Server 2022** | |
| .NET Framework 3.5, 4.8 | [5126050](https://support.microsoft.com/kb/5126050) |

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| .NET Framework 3.5, 4.8.1 | [5126422](https://support.microsoft.com/kb/5126422) |

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| **Windows 10, version 22H2** | |
| .NET Framework 3.5, 4.8 | [5126046](https://support.microsoft.com/kb/5126046) |

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| .NET Framework 3.5, 4.8.1 | [5126421](https://support.microsoft.com/kb/5126421) |

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| **Windows 10, version 21H2** | |
| .NET Framework 3.5, 4.8 | [5126046](https://support.microsoft.com/kb/5126046) |

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| .NET Framework 3.5, 4.8.1 | [5126421](https://support.microsoft.com/kb/5126421) |

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| **Windows 10 1809 and Windows Server 2019** | |
| .NET Framework 3.5, 4.7.2 | [5126043](https://support.microsoft.com/kb/5126043) |

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| .NET Framework 3.5, 4.8 | [5126048](https://support.microsoft.com/kb/5126048) |

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| **Windows 10 1607 and Windows Server 2016** | |
| .NET Framework 3.5, 4.6.2, 4.7, 4.7.1, 4.7.2 | Pending package; will be included in the LCU |
| .NET Framework 4.8 | [5126047](https://support.microsoft.com/kb/5126047) |

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The following table is for earlier Windows Server versions for Security and Quality Rollup updates.

| Product version | Security and quality rollup |
| --- | --- |
| **Windows Server 2012 R2** | |
| .NET Framework 3.5 | [5120695](https://support.microsoft.com/kb/5120695) |
| .NET Framework 4.6.2, 4.7, 4.7.1, 4.7.2 | [5126045](https://support.microsoft.com/kb/5126045) |

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| .NET Framework 4.8 | [5126051](https://support.microsoft.com/kb/5126051) |

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| **Windows Server 2012** | |
| .NET Framework 3.5 | [5120716](https://support.microsoft.com/kb/5120716) |
| .NET Framework 4.6.2, 4.7, 4.7.1, 4.7.2 | [5126044](https://support.microsoft.com/kb/5126044) |

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| .NET Framework 4.8 | [5126049](https://support.microsoft.com/kb/5126049) |

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The operating system rows list a KB that's used for update-offering purposes. When the operating system KB is offered, the applicability logic determines the specific .NET Framework updates that will be installed. Updates for individual .NET Framework versions are installed based on the version of .NET Framework that's already present on the device. Because of this, the operating system KB is not expected to be listed as an installed update on the device. The expected updates to be installed are the .NET Framework specific version updates listed in the preceding table.

This update installs the complete .NET Framework 3.5 product for Windows 11, version 26H1 (build version 28000) and newer. Unlike traditional cumulative updates that patch individual components, this update delivers the full .NET Framework 3.5 product as a standalone installer. It replaces any previously installed version.

| Product version | .NET Framework 3.5 product update |
| --- | --- |
| .NET Framework 3.5 | [5120747](https://support.microsoft.com/kb/5120747) |
3 changes: 2 additions & 1 deletion docs/framework/release-notes/release-notes.md
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Expand Up @@ -11,7 +11,8 @@ The .NET Framework updates include cumulative security and reliability improveme

.NET Framework cumulative update releases are discussed in detail in the following individual release notes:

* August 27, 2026 - [cumulative update preview](./2026/08-27-august-cumulative-update-preview.md) **New Release**
* September 8, 2026 - [cumulative update](./2026/09-08-september-cumulative-update.md) **New Release**
* August 27, 2026 - [cumulative update preview](./2026/08-27-august-cumulative-update-preview.md)
* August 11, 2026 - [cumulative update](./2026/08-11-august-cumulative-update.md)
* July 14, 2026 - [cumulative update](./2026/07-14-july-cumulative-update.md)
* May 26, 2026 - [cumulative update preview](./2026/05-26-may-cumulative-update-preview.md)
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2 changes: 2 additions & 0 deletions docs/framework/toc.yml
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items:
- name: Overview and index
href: release-notes/release-notes.md
- name: September 2026 cumulative update
href: release-notes/2026/09-08-september-cumulative-update.md
- name: August 2026 cumulative update preview
href: release-notes/2026/08-27-august-cumulative-update-preview.md
- name: August 2026 cumulative update
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