KB5120418: Cumulative update for Windows 10, version 1607, August 2026. Exploited WinSock driver flaw patched; File History backups restored

An exploited WinSock driver flaw is patched, and failed File History network backups are fixed. Secure Boot certificate updates continue to reach eligible devices.

Does it affect you? Applies to: Devices running Windows 10, version 1607: Enterprise LTSB 2016 or IoT Enterprise 2016 LTSB.

Microsoft publishes separate notes for this KB for Windows Server.

What changes

Fix 1 change

Backup

File History backups to network shares work again instead of failing with an incorrect credentials error.¹
Resolves failures in automatic File History backups to network shares using Server Message Block (SMB); scheduled backups might not copy any files when the error occurs.

Improvement 1 change

Secure Boot

Gradual rollout Verified in package

For: Supported PCs and non-managed business devices

More devices can receive updated Secure Boot certificates automatically. The rollout continues over the coming months.²
Adds high-confidence device-targeting data, increasing coverage of devices eligible to automatically receive new Secure Boot certificates. Deployment continues across supported PCs and non-managed business devices.

Technical details

Data sheet · Security · Downloads · Components Click to collapse or expand

Data sheet

Released: 2026-08-11
Classification: Security Updates
Type: Cumulative update
Restart: Required
Replaces: KB5099535, KB5094122, KB5087537, KB5091572

+21 earlier
KB5082198, KB5078938, KB5075999, KB5073722, KB5074974, KB5071543, KB5068864, KB5066836, KB5065427, KB5063871, KB5062560, KB5061010, KB5058383, KB5058921, KB5055521, KB5053594, KB5052006, KB5049993, KB5048671, KB5046612, KB5037423
Replaced by: KB5123099

Version	Build	Channel
1607	14393.9418	General availability

Security

147 vulnerabilities fixed

1 exploited 11 critical 136 important

Vulnerability	Severity	CVSS
CVE-2026-68820 Exploited Windows Ancillary Function Driver for WinSock Elevation of Privilege Vulnerability	Important	7.0
CVE-2026-65791 Windows iSCSI Target Service Remote Code Execution Vulnerability	Critical	9.8
CVE-2026-62816 Windows Reliable Multicast Transport Driver (RMCAST) Remote Code Execution Vulnerability	Critical	8.8
CVE-2026-62818 Windows Active Directory Certificate Services (AD CS) Remote Code Execution Vulnerability	Critical	8.8
CVE-2026-62822 Windows GDI+ Remote Code Execution Vulnerability	Critical	8.8
CVE-2026-62824 Remote Desktop Client Remote Code Execution Vulnerability	Critical	8.8
CVE-2026-62819 Windows Routing and Remote Access Service (RRAS) Remote Code Execution Vulnerability	Critical	8.1
CVE-2026-62889 Windows Secure Socket Tunneling Protocol (SSTP) Remote Code Execution Vulnerability	Critical	8.1
CVE-2026-65679 Windows iSCSI Target Service Remote Code Execution Vulnerability	Critical	8.1
CVE-2026-65796 Windows iSCSI Target Service Remote Code Execution Vulnerability	Critical	8.1
CVE-2026-62890 Windows GDI+ Elevation of Privilege Vulnerability	Critical	7.8
CVE-2026-66799 Windows Key Guard Elevation of Privilege Vulnerability	Critical	7.8

The table lists the 12 exploited, publicly disclosed or critical vulnerabilities. See all 147 vulnerabilities →

Downloads (Microsoft Update Catalog)

x64 1607

1.8 GB

windows10.0-kb5120418-x64.msu Main update · KB5120418 SHA-1: 01010497…58dfca

x86 1607

1.0 GB

windows10.0-kb5120418-x86.msu Main update · KB5120418 SHA-1: 847a65b8…df3fa4

Updated components

1,072 files changed since the previous update for the same versions.

Top changed components	Files
WPF	28
Networking	21
Remote Desktop	16
Graphics and display	14
Secure Boot	14
Security and sign-in	13
ASP.NET	12
Hyper-V and virtualization	8
Kernel	8
Search	8
Audio	7
File Explorer and shell	6

Verified in package: changed files confirm Secure Boot.

Page history

Nov 11, 2026

Added 7 vulnerabilities (7 important)
Nov 9, 2026

Removed CVE-2026-62740

Removed CVE-2026-62752

Removed CVE-2026-62800

Removed CVE-2026-62877

Removed CVE-2026-70344

Sources

Microsoft Support: KB5120418

Updated Nov 11, 2026

Cited passages from Microsoft's official notes (2)

1. [Backup] File History automatic backups to network shares using Server Message Block (SMB) might fail with an incorrect "invalid credentials" error. When this issue occurs, scheduled backups do not copy any files. This update resolves the issue. support.microsoft.com
2. [Secure Boot] This update includes additional high confidence device targeting data, increasing coverage of devices eligible to automatically receive new Secure Boot certificates. Certificate deployment via Windows updates continues across supported PCs and non-managed business devices in the coming months. support.microsoft.com

Checked automatically: 8 of 8 checks passed, 2 quoted passages · compared with Microsoft's page on Sep 25, 2026

Quotes found in the official pages: passed
Numbers found in the sources: passed
Vulnerabilities from the dossier only: passed
Links to allowed domains only: passed
Every official change covered: passed
Readable plain text: passed
Changes confirmed by the file list: passed
Sources agree: passed

A second AI read the text against the sources: correctness 5/5, clarity 4/5, completeness 5/5. How we work

Published by The Update Bureau. Written with AI from Microsoft's own documents, checked by rules and a second AI. How we work · Report a mistake