Windows Network Address Translation (NAT) Spoofing Vulnerability

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

According to the CVSS metric, the attack vector is adjacent (AV:A). What does that mean for this vulnerability? This vulnerability's attack is limited at the protocol level to a logically adjacent topology. This means it cannot simply be done across the internet, but instead needs something specific tied to the target. Good examples would include the same shared physical network (such as Bluetooth or IEEE 802.11), logical network (local IP subnet), or from within a secure or otherwise limited administrative domain (MPLS, secure VPN to an administrative network zone). This is common to many attacks that require machine-in-the-middle (MITM) type setups or that rely on initially gaining a foothold in another environment.

According to the CVSS metric, the attack complexity is high (AC:H). What does that mean for this vulnerability? The attacker must inject themselves into the logical network path between the target and the resource requested by the victim to read or modify network communications. This is called a machine-in-the-middle (MITM) attack.

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 key and reboot the machine. reg add HKLM\SYSTEM\CurrentControlSet\Services\Winnat /v DisableFailOver /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.

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 · 5099536 (opens in a new tab)
• Microsoft remediation guidance (opens in a new tab)
• Microsoft security update · 5101650 (opens in a new tab)
• Microsoft remediation guidance (opens in a new tab)
• Microsoft security update · 5101649 (opens in a new tab)
• Microsoft remediation guidance (opens in a new tab)