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Windows Server 2019 Windows Server 2019 Security update
Patch Tuesday Zero-day

KB5073723

KB5073723: Cumulative update for Windows Server, version 2019, January 2026. Exploited DWM flaw patched; modem drivers removed

In short

An actively exploited Desktop Window Manager flaw is patched. The update also removes several modem drivers, so hardware that depends on them stops working.

Does it affect you? Applies to: Devices running Windows Server 2019. The listed update package is for x64 systems.

Build
17763.8276
Security
72 fixed · 1 critical · 1 exploited
Restart
Required

Microsoft publishes separate notes for this KB for Windows 10.

What changes

Improvements 3 changes

Credentials autofill

  • Credential dialogs ignore virtual keyboard input from remote access tools during some remote support or automated sign-in sessions.1
    The security hardening behavior restricts certain applications from autofilling credentials during remote support sessions or automated authentication workflows.

Windows Deployment Services (WDS)

For: IT administrators using WDS

  • Hands-free deployment is no longer supported by default. Administrators should follow Microsoft's guidance.2
    WDS changes behavior so hands-free deployment is disabled by default.

Servicing stack

  • The component that installs Windows updates gets quality improvements.3
    The package includes servicing stack update KB5074222, build 17763.8260.

Fix 1 change

WinSqlite3.dll

For: Devices where security software flagged WinSqlite3.dll

  • The Windows component that some security software flagged as vulnerable is updated.4
    Updates the Windows core component WinSqlite3.dll. The page distinguishes it from application-specific sqlite3.dll files.

Removal 1 change

Drivers

For: Devices using these modem drivers

  • Modems that rely on four listed drivers stop working because the update removes those drivers.5
    Removes agrsm64.sys (x64), agrsm.sys (x86), smserl64.sys (x64), and smserial.sys (x86).

Known issues

  1. Resolved Affects: Everyone Resolved by KB5082123

    Japanese characters fail to render correctly in PowerShell

    Japanese text might appear garbled or as question marks in PowerShell on Japanese-language installations. This issue is resolved by updates released on or after April 14, 2026, such as KB5082123.6

    Resolution Fixed in KB5082123

    Install KB5082123 (or a later cumulative update) on affected devices. No manual workaround is required after updating.

  2. Resolved Affects: Everyone Resolved by KB5075904

    Some devices with Virtual Secure Mode enabled might fail to shut down or hibernate

    Some Secure Launch-capable PCs with Virtual Secure Mode enabled might restart instead of shutting down or entering hibernation. KB5075904 addresses this issue.7

    Resolution Fixed in KB5075904

    Install KB5075904 (or a later cumulative update) on affected devices. No manual workaround is required after updating.

  3. Open Affects: Everyone

    Apps might become unresponsive when saving files to cloud-based storage

    Some apps might hang or show errors when opening files from or saving files to cloud storage. The issue remains open; KB5078131 is listed as a workaround.8

    How to apply the workaround Workaround

    Install KB5078131, which the page lists as addressing the issue.8

  4. Resolved Affects: Everyone Resolved by KB5077795

    Connection and authentication failures in Azure Virtual Desktop and Windows 365

    Some Windows App connections to Azure Virtual Desktop or Windows 365 might fail at sign-in. This issue is resolved by updates released on or after January 17, 2026, such as KB5077795.9

    Resolution Fixed in KB5077795

    Install KB5077795 (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
2026-01-13
Classification
Security Updates
Type
Cumulative update
Restart
Required
Replaces
KB5074975, KB5071544, KB5068791, KB5070883
+12 earlier KB5066586, KB5065428, KB5066187, KB5063877, KB5062557, KB5060531, KB5061978, KB5058392, KB5059091, KB5058922, KB5050008, KB5037425
Replaced by
KB5077795
VersionBuildChannel
2019 17763.8276 General availability

Security

72 vulnerabilities fixed
1 exploited 1 critical 70 important 1 not rated
VulnerabilitySeverityCVSS
CVE-2026-20805 Exploited
Desktop Window Manager Information Disclosure Vulnerability
 Important 5.5
CVE-2026-20822
Windows Graphics Component Elevation of Privilege Vulnerability
 Critical 7.8
CVE-2023-31096
MITRE: CVE-2023-31096 Windows Agere Soft Modem Driver Elevation of Privilege Vulnerability
 Important 7.8
CVE-2026-21265
Secure Boot Certificate Expiration Security Feature Bypass Vulnerability
 Important 6.4

The table lists the 4 exploited, publicly disclosed or critical vulnerabilities. See all 72 vulnerabilities →

Downloads (Microsoft Update Catalog)

x64 2019
716.6 MB
windows10.0-kb5073723-x64.msu Main update · KB5073723 SHA-1: 0a9c8dd8…3e6851

Updated components

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

Top changed componentsFiles
Graphics and display13
Security and sign-in12
Hyper-V and virtualization11
Networking10
Bluetooth8
Kernel7
File Explorer and shell6
Search5
Storage and file systems5
Secure Boot4
Audio3
Remote Desktop3

Sources

Updated
Cited passages from Microsoft's official notes (9)
  1. 1. credential dialogs do not respond to virtual keyboard input from remote desktop or screen sharing tools or apps. support.microsoft.com
  2. 2. This update introduces a change in behavior in which WDS will stop supporting hands-free deployment functionality by default. support.microsoft.com
  3. 3. This update makes quality improvements to the servicing stack, which is the component that installs Windows updates. support.microsoft.com
  4. 4. Fixed: The Windows core component, WinSqlite3.dll, has been updated. support.microsoft.com
  5. 5. This update removes the following modem drivers: agrsm64.sys (x64), agrsm.sys (x86), smserl64.sys (x64) and smserial.sys (x86). support.microsoft.com
  6. 6. This issue is resolved in Windows updates released on and after April 14, 2026 (such as KB5082123). support.microsoft.com
  7. 7. This issue is addressed in KB5075904. support.microsoft.com
  8. 8. This issue is addressed in KB5078131. support.microsoft.com
  9. 9. This issue is resolved in Windows updates released on and after January 17, 2026 (such as KB5077795). support.microsoft.com
Checked automatically: 8 of 8 checks passed, 9 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 4/5, clarity 4/5, completeness 4/5. 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