October 2025 Microsoft Update Summary
October 2025 brought a series of critical security and stability improvements across the Microsoft ecosystem. Updates released for Windows 10, Windows 11, and Windows Server versions include essential
Windows 10 – October 14, 2025—KB5066791 (OS Builds 19044.6456 and 19045.6456)
Windows 10, version 21H2 This security update includes fixes and quality improvements from the following updates:
September 9, 2025—KB5065429 (OS Builds 19044.6332 and 19045.6332)
September 25, 2025—KB5066198 (OS Build 19045.6395) Preview
[Input and Composition]
Fixed: An issue in the Chinese Input Method Editor (IME) where custom Unicode characters displayed incorrectly and did not meet the GB18030 standard.
Fixed: An issue affecting USER32 Edit controls. When text fields reached length limits, surrogate pairs appeared as empty boxes.
[Windows Remote Management (WinRM)]
Fixed: An issue affecting PowerShell Remoting and WinRM, causing commands to time out after 600 seconds.
[Licensing]
New! This update introduces a Servicing Stack Update (SSU) that includes an updated certificate chain to improve Azure environment validation.
[Fax Modem Driver]
This update removes the ltmdm64.sys driver. Fax modem hardware that relies on this driver will no longer function in Windows.
Windows 10, version 22H2 This security update includes fixes and quality improvements from the following updates:
September 9, 2025—KB5065429 (OS Builds 19044.6332 and 19045.6332)
September 25, 2025—KB5066198 (OS Build 19045.6395) Preview
(Same fixes as above.)
Windows 10 – October 14, 2025—KB5066586 (OS Build 17763.7919)
Windows 10, version 1809 / Windows Server 2019 This security update includes the following improvements:
Fixed: IME issue with custom Unicode characters not conforming to GB18030.
Fixed: USER32 Edit control issue causing surrogate pairs to appear as boxes.
Fixed: WinRM timeout issue (600 seconds).
Fixed: Stability issue introduced after May 2025 updates, causing devices to become unresponsive in rare cases.
Removed ltmdm64.sys fax modem driver.
Windows 10 – October 14, 2025—KB5066836 (OS Build 14393.8519)
Windows 10, version 1607 / Windows Server 2016 Includes the same WinRM timeout fix, system stability improvements, and removal of ltmdm64.sys.
Windows 10 initial version – October 14, 2025—KB5066837 (OS Build 10240.21161)
Windows 10, version 1507 Includes the removal of ltmdm64.sys fax modem driver.
Windows 11, version 25H2 – October 14, 2025—KB5066835 (OS Builds 26200.6899 and 26100.6899)
Includes fixes from KB5065789 (September 29, 2025):
Fixed: Issue causing print preview in Chromium-based browsers to stop responding.
Fixed: Gamepad-only sign-in issue where later inputs stopped responding.
Fixed: PowerShell remote command timeouts after 10 minutes.
Fixed: Windows Hello setup issue with USB IR cameras showing repeated “Make sure your face is centered” errors.
Removed ltmdm64.sys driver (fax modems no longer supported).
Known Issues: Some BluRay/DVD/Digital TV apps may fail to play protected content after KB5064081 or later. HDCP-related DRM apps may show copyright errors, playback interruptions, or black screens. Streaming services are not affected. Partial fix included in KB5065789; further updates recommended.
Windows 11, version 23H2 – October 14, 2025—KB5066793 (OS Builds 22621.6060 and 22631.6060)
Includes all enhancements from version 22H2.
Windows Server 2022 – October 14, 2025—KB5066782 (OS Build 20348.4294)
Includes IME display fixes, NetBIOS SMBv1 connectivity fix, PowerShell WinRM timeout fix, system stability fixes, McpManagement service bug fix, and ltmdm64.sys removal.
Office and SharePoint Updates (October 14, 2025)
SharePoint Server 2019 / 2016 Fixes multiple Remote Code Execution (RCE) and Information Disclosure vulnerabilities (CVE-2025-59221 through CVE-2025-59238). Adds AMSI scanning for HTTP requests and restores workflow functionality through PowerShell commands.
Office 2016 (Excel, Word, PowerPoint, Access, Visio) Fixes RCE and information disclosure vulnerabilities (CVE-2025-59221 to CVE-2025-59238).
Office Online Server Fixes multiple RCE vulnerabilities in Excel components (CVE-2025-59223 to CVE-2025-59236).
Internet Explorer (KB5066840) Security update addressing multiple vulnerabilities in IE 9 and 11 across Windows Server versions.
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