Executive brief
A security vulnerability exists in the Windows Network Address Translation (NAT) service, which manages how devices on a local network share a single internet connection. An attacker located on the same local network could exploit this flaw to impersonate other systems or intercept sensitive communications. This could lead to a total loss of confidentiality and data integrity for affected systems, though the attack requires specific network conditions to be successful.
Technical details
A vulnerability classified as an Origin Validation Error (CWE-346) exists in the Windows Network Address Translation (NAT) component. The flaw allows an unauthenticated attacker on the same local or adjacent network to perform spoofing attacks due to improper validation of the source of network traffic. While the attack vector is adjacent, the complexity is rated as high, suggesting specific environmental conditions or timing are required for successful exploitation. If successful, the attacker can achieve a scope-crossing impact with high consequences for confidentiality, integrity, and availability. Microsoft has released security updates to address this issue across affected versions of Windows 11 and Windows Server 2025.
Affected products
- Microsoft Windows 11 Version 24H2 10.0.26100.0 to 10.0.26100.8875
- Microsoft Windows 11 Version 25H2 10.0.26200.0 to 10.0.26100.8875
- Microsoft Windows 11 version 26H1 10.0.28000.0 to 10.0.28000.2525
- Microsoft Windows Server 2025 10.0.26100.0 to 10.0.26100.33158
Timeline
- 2026-07-14: disclosed
- 2026-07-14: advisory