Windows Network Address Translation (NAT) Spoofing Vulnerability
Published August 11, 2026Updated August 11, 2026
Source data
Overview
Origin validation error in Windows Network Address Translation (NAT) allows an unauthorized attacker to perform spoofing over an adjacent network.
Impact & technical details
Spoofing
- CVSS base score
- 8.3 / 10
- CVSS vector
- CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H/E:U/RL:O/RC:C
Highest base score supplied by MSRC for this record; the vector belongs to that score. Ratings can vary by product. Microsoft Important is displayed as High; Moderate is displayed as Medium.
Affected products
- Windows 11 Version 24H2 for ARM64-based Systems
- Windows 11 Version 24H2 for x64-based Systems
- Windows 11 Version 25H2 for ARM64-based Systems
- Windows 11 Version 25H2 for x64-based Systems
- Windows 11 Version 26H1 for ARM64-based Systems
- Windows 11 version 26H1 for x64-based Systems
- Windows Server 2025
- Windows Server 2025 (Server Core installation)
Source guidance
Remediation
- The mitigation is disabled by default. To enable it, apply the following registry keys and reboot the machine. reg add HKLM\SYSTEM\CurrentControlSet\Services\Winnat /v TcpSeqValidation /t REG_DWORD /d 1 /f reg add HKLM\SYSTEM\CurrentControlSet\Services\Winnat /v TcpSeqRandomization /t REG_DWORD /d 1 /f
At least one Microsoft vendor-fix reference is available. Check each affected product for its applicable update, prerequisites, and supported version.
GTP recommendation · Rule-based guidance
Recommended next step
Review affected Microsoft products and apply the applicable security updates through your organization's normal patch-management process. Confirm availability and prerequisites in the Microsoft advisory.
Authoritative sources & updates
Findings and update information come from the linked publishers. GTP compiles the public record and provides the recommendation above. CVSS ratings shown here come from Microsoft. NVD references provide additional public context.
- Microsoft Security Response Center (opens in a new tab)
- Microsoft security update · 5120233 (opens in a new tab)
- Microsoft remediation guidance (opens in a new tab)
- Microsoft security update · 5120228 (opens in a new tab)
- Microsoft remediation guidance (opens in a new tab)
- Microsoft security update · 5121003 (opens in a new tab)
- Microsoft remediation guidance (opens in a new tab)
- Microsoft security update · 5120994 (opens in a new tab)
- Microsoft remediation guidance (opens in a new tab)
- Microsoft security update · 5121000 (opens in a new tab)
- Microsoft remediation guidance (opens in a new tab)
Managed by GTP?
Griffin Technology Partners managed customers may receive additional environment-specific security guidance and remediation assistance through their managed services relationship.
Security bulletins are provided for informational purposes and compiled from authoritative public sources. Vulnerability applicability varies by environment. Validate affected products, configuration, compatibility requirements, and vendor guidance before making production changes.