# Microsoft Office 2021 end of support

> Live situation record from CLSTR: https://clstr.news/situations/microsoft-office-2021-end-of-support
> Updated: 2026-09-14T07:58:00.000Z. Sources: 26. Developments: 2.

Microsoft has confirmed that official support for Office 2021 will end on October 13, 2026. Following this date, applications including Word, Excel, and PowerPoint will no longer receive security updates or extended support programs. Microsoft has not announced an official paid Extended Security Update (ESU) program for this software, instead encouraging users to migrate to Microsoft 365 or Office 2024.

To mitigate security risks, the firm 0patch has announced it will provide third-party security support for Office 2021 for at least three years starting from the official end-of-life date. This service utilizes “micropatches,” which are lightweight code fragments injected directly into a computer's memory during program execution. This method allows for the correction of critical vulnerabilities without modifying original files or requiring system restarts.

0patch offers these services through Pro and Enterprise subscription plans. The Pro plan is priced at approximately 24.95 euros plus VAT per computer annually, while the Enterprise version provides centralized management and single sign-on capabilities for larger organizations.

## Claims

- Certain USB Audio Class 1.0 devices failed when using multichannel, 8-channel, or 3D audio modes. (corroborated by 14 sources)
- The September security update caused Remote Desktop Services (RDS) to become unstable, leading to connection failures and login errors. (corroborated by 13 sources)
- Microsoft released out-of-band updates to address issues caused by the September 2026 security update. (corroborated by 11 sources)
- Hyper-V users experienced issues where host folders shared via the Plan9 protocol were inaccessible in Linux virtual machines. (corroborated by 10 sources)
- System tools including File Explorer and the Microsoft Management Console (MMC) became unresponsive following the September update. (corroborated by 10 sources)
- The emergency updates include security fixes for privilege escalation vulnerabilities, such as CVE-2026-62721. (corroborated by 6 sources)

## Timeline

### 2026-09-14: Microsoft releases emergency Windows updates to fix Remote Desktop and Hyper-V bugs

Microsoft issued emergency out-of-band updates for Windows 11 and Server to fix Remote Desktop instability, Hyper-V folder-sharing bugs, and USB audio failures caused by the September 2026 security patch.

23 sources. https://clstr.news/cluster/0patch-to-provide-security-updates-for-office-2021-after-microsoft-end-of-support

### 2026-09-08: Microsoft to end Office 2021 support in 2026

Microsoft will end official support for Office 2021 on October 13, 2026. ACROS Security's 0patch platform offers a way to extend secure usage until 2029 via memory-based security patches.

3 sources. https://clstr.news/cluster/microsoft-to-end-office-2021-support-in-2026

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Cite as: Microsoft Office 2021 end of support. CLSTR, https://clstr.news/situations/microsoft-office-2021-end-of-support