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Windows 10 1607 Windows 10 1607 Security update
Patch Tuesday

KB5049993

KB5049993: Cumulative update for Windows 10, version 1607, January 2025. Critical OLE and multicast code-execution flaws addressed

In short

The update adds drivers to the vulnerable-driver blocklist and addresses 105 security vulnerabilities, including five critical ones. CVE-2025-21308, a Windows Themes spoofing flaw, was publicly disclosed.

Does it affect you? Applies to: Devices running Windows 10 Enterprise LTSB 2016, version 1607. Packages are available for x86 and x64 devices.

Build
14393.7699
Security
105 fixed · 5 critical
Restart
Required

Microsoft publishes separate notes for this KB for Windows Server.

What changes

Improvement 1 change

Windows Kernel Vulnerable Driver Blocklist file (DriverSiPolicy.p7b)

Verified in package
  • The blocklist covers more drivers that are at risk of attacks using vulnerable drivers.1
    Adds drivers to the Windows Kernel Vulnerable Driver Blocklist file (DriverSiPolicy.p7b) to address Bring Your Own Vulnerable Driver (BYOVD) attacks.

Known issues

  1. Resolved Affects: Everyone Resolved by KB5052006

    After installing this security update, you might experience issues with USB audio devices.

    USB audio devices might stop working and prevent audio playback, especially when the setup uses a DAC (digital-to-analog converter) based on a USB 1.0 audio driver. Device Manager might show Code 10, “Insufficient system resources exist to complete the API.” KB5052006 addresses this issue.2

    Resolution Fixed in KB5052006

    Install KB5052006 (or a later cumulative update) on affected devices. No manual workaround is required after updating.

Technical details

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

Data sheet

Released
2025-01-14
Classification
Security Updates
Type
Cumulative update
Restart
Required
Replaces
KB5048671, KB5046612, KB5037423
Replaced by
KB5052006
VersionBuildChannel
1607 14393.7699 General availability

Security

105 vulnerabilities fixed
5 critical 100 important
VulnerabilitySeverityCVSS
CVE-2025-21298
Windows OLE Remote Code Execution Vulnerability
 Critical 9.8
CVE-2025-21307
Windows Reliable Multicast Transport Driver (RMCAST) Remote Code Execution Vulnerability
 Critical 9.8
CVE-2025-21294
Microsoft Digest Authentication Remote Code Execution Vulnerability
 Critical 8.1
CVE-2025-21295
SPNEGO Extended Negotiation (NEGOEX) Security Mechanism Remote Code Execution Vulnerability
 Critical 8.1
CVE-2025-21296
BranchCache Remote Code Execution Vulnerability
 Critical 7.5
CVE-2025-21308
Windows Themes Spoofing Vulnerability
 Important 6.5

The table lists the 6 exploited, publicly disclosed or critical vulnerabilities. See all 105 vulnerabilities →

Updated components

545 files changed since the previous update for the same versions.

Top changed componentsFiles
Networking24
Secure Boot17
Security and sign-in13
.NET runtime (CLR)12
File Explorer and shell10
Search10
Kernel9
Graphics and display6
Hyper-V and virtualization6
Storage and file systems6
Audio2
Emoji and input2

Verified in package: changed files confirm Windows Kernel Vulnerable Driver Blocklist file (DriverSiPolicy.p7b).

Sources

Updated
Cited passages from Microsoft's official notes (2)
  1. 1. This update adds to the list of drivers that are at risk for Bring Your Own Vulnerable Driver (BYOVD) attacks. support.microsoft.com
  2. 2. This issue is addressed in KB5052006. support.microsoft.com
Checked automatically: 8 of 8 checks passed, 2 quoted passages · compared with Microsoft's page on Oct 21, 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