# CVE-2026-56181: Microsoft Windows NAT origin validation error spoofing

Source: https://junglewise.ai/threats/cve-2026-56181-microsoft-windows-nat-origin-validation-error-spoofing  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-14. Updated: 2026-07-14  
License: CC BY 4.0 with a link back

CVE-2026-56181 · Severity: high · CVSS 8.3 · Published 2026-07-14

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.

Technologies: [Microsoft Windows 11](https://junglewise.ai/threats/technologies/windows-11), [Microsoft Windows Server 2025](https://junglewise.ai/threats/technologies/windows-server-2025). Vendors: [Microsoft](https://junglewise.ai/threats/vendors/microsoft).

## Quick answers

**Is CVE-2026-56181 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-56181 being exploited in the wild.

**How severe is CVE-2026-56181?** High severity, with a CVSS score of 8.3, published 14 July 2026.

**Which products and versions are affected?** Microsoft Windows 11 10.0.26100.0 to 10.0.26100.8875; Microsoft Windows Server 2025 10.0.26100.0 to 10.0.26100.33158.

**Is there a fix for CVE-2026-56181?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-56181 attacked?** It is attacked from the adjacent network, in an operating system.

**Am I affected by CVE-2026-56181?** Check whether you run Microsoft Windows 11 or Microsoft Windows Server 2025 at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## 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

## References

- [https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-56181](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-56181)

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