Microsoft released KB5078938 on March 10, 2026, a cumulative security update for Windows 10 Version 1607 and Windows Server 2016 that raises the operating system build to 14393.8957. The update is part of the March Patch Tuesday cycle and addresses vulnerabilities across several core Windows components.
Because Windows Server 2016 is still common in production, admins running the 14393 branch need to plan deployment to close privilege-escalation, remote code execution and authentication-bypass exposures described for this update.
Key takeaways
- KB5078938 was released on March 10, 2026 for Windows 10 1607 and Windows Server 2016.
- The update moves affected systems to build 14393.8957.
- It addresses kernel privilege escalation, networking-stack RCE, authentication bypass, information disclosure and denial-of-service issues.
- Windows 10 1607 coverage is limited to Enterprise and Education editions still in extended support.
- Roughly 1.2 GB of free disk space and a restart are required to install.
Affected
What KB5078938 is
KB5078938 is a cumulative security update released on March 10, 2026 for Windows 10 Version 1607 and Windows Server 2016. It updates affected systems to build 14393.8957 and is delivered as part of Microsoft's regular Patch Tuesday cadence.
According to the update documentation, KB5078938 resolves multiple vulnerability categories in core Windows components. Systems on the 14393 branch that skip the update remain exposed to the issues it addresses.
- New OS build after install: 14393.8957
- Release date: March 10, 2026
Vulnerabilities addressed
The update documentation describes fixes spanning several vulnerability classes rather than naming individual CVEs in the extracted material:
- Windows kernel privilege escalation that could let local attackers gain SYSTEM-level rights.
- Remote code execution in the Windows networking stack via specially crafted network packets, potentially without user interaction.
- Authentication bypass in Windows authentication mechanisms affecting local and network scenarios.
- Information disclosure that could expose memory contents, configuration details or user data.
- Denial-of-service conditions that could crash systems or make them unresponsive.
The documentation attributes the root causes to improper input validation, memory-management issues and insufficient access controls, including inadequate bounds checking in kernel-mode drivers and weak validation of network protocol messages.
CVE details not in source
The extracted material does not list specific CVE identifiers, CVSS scores or exploitation status. Confirm those details against Microsoft's official Security Update Guide before risk-rating.
Affected systems
KB5078938 applies to the following operating systems and editions, all moving to build 14393.8957:
- Windows 10 Version 1607, 32-bit (x86)
- Windows 10 Version 1607, 64-bit (x64)
- Windows Server 2016, 64-bit (x64)
- Windows Server 2016 (Server Core), 64-bit (x64)
Editions matter for Windows 10 1607
Windows 10 Version 1607 reached end of service for Home and Pro editions in April 2018. This update primarily targets Enterprise and Education editions that continue to receive extended support.
Deployment and verification
Distribution channels
- Windows Update: automatically delivered to eligible systems.
- Microsoft Update Catalog: manual download for controlled deployments (search for KB5078938).
- WSUS: appears under the Security Updates classification for approval.
- SCCM: deployable through software update management workflows as a high-priority security update.
Requirements
- No specific prerequisite updates required.
- Approximately 1.2 GB free disk space (1.5 GB recommended to avoid failures).
- System restart required to complete installation.
- Typical install time of 15-30 minutes depending on hardware.
Verify installation
Get-HotFix -Id KB5078938
Get-ComputerInfo | Select-Object WindowsVersion, WindowsBuildLabExAfter a successful install, the build number should read 14393.8957.
Known issues
- Installation may fail with error 0x80070643 when disk space is insufficient; ensure at least 1.5 GB free on the system drive.
- A small number of systems may see temporary network connectivity issues immediately after restart, usually clearing within 2-3 minutes.
- Legacy apps relying on deprecated authentication methods may need vendor updates for compatibility.
- Systems with under 4 GB RAM may see brief performance degradation that typically normalizes within 24 hours.
If persistent problems occur, the update can be removed via Settings > Update & Security > Windows Update > View update history > Uninstall updates.
Timeline
Impact & actions
Systems left unpatched on the 14393 branch remain exposed to privilege escalation, remote code execution, authentication bypass, information disclosure and denial-of-service issues.
Security: Closes multiple vulnerability classes including kernel privilege escalation and networking-stack remote code execution.
Privacy: Addresses information disclosure vulnerabilities that could expose sensitive system or user data.
Recommended actions · High urgency
- 1Deploy KB5078938 to all Windows 10 1607 and Windows Server 2016 systems
- 2Ensure at least 1.5 GB free disk space before installation
- 3Verify the resulting build shows 14393.8957
- 4Confirm specific CVEs and severity against Microsoft's Security Update Guide
Technical details
- Affected versions
- Windows 10 Version 1607 (pre-14393.8957), Windows Server 2016 (pre-14393.8957)
- Patched versions
- 14393.8957
Mitigations
- Install KB5078938 via Windows Update, WSUS, SCCM or the Microsoft Update Catalog
Response
Customer guidance
Microsoft's documentation recommends applying the update via automated update mechanisms, maintaining defense-in-depth controls such as network segmentation, monitoring for unusual activity, and keeping anti-malware solutions current.
FAQ
What does KB5078938 resolve?
It resolves multiple security vulnerabilities in Windows 10 Version 1607 and Windows Server 2016, including kernel privilege escalation, remote code execution in networking components, authentication bypass, information disclosure and denial-of-service issues. The update brings the OS build to 14393.8957.
Which systems require KB5078938?
It applies to Windows 10 Version 1607 (32-bit and 64-bit), Windows Server 2016 and Windows Server 2016 Server Core. For Windows 10 1607, coverage is limited to Enterprise and Education editions still in extended support.
How do I confirm KB5078938 is installed?
Run Get-HotFix -Id KB5078938 in PowerShell, and confirm the OS build reports 14393.8957 after a restart.
How much disk space does the update need?
About 1.2 GB is required, but Microsoft advises at least 1.5 GB free on the system drive to avoid installation failures such as error 0x80070643.
The bottom line
KB5078938, released March 10, 2026, updates Windows 10 Version 1607 and Windows Server 2016 to build 14393.8957 and fixes several classes of security vulnerabilities.
What happens next
What to do
