CVE-2026-56181

Analyzed Analyzed - Analysis Complete

Windows NAT Spoofing Vulnerability

Publication date: 2026-07-14

Last updated on: 2026-07-22

Assigner: Microsoft Corporation

Description

Origin validation error in Windows Network Address Translation (NAT) allows an unauthorized attacker to perform spoofing over an adjacent network.

CVSS Scores

EPSS Scores

Probability:
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Meta Information

Published

2026-07-14

Last Modified

2026-07-22

Generated

2026-08-04

AI Q&A

2026-07-15

EPSS Evaluated

2026-08-02

NVD

CVE-2026-56181

EUVD

EUVD-2026-44316

Affected Vendors & Products

Vendor	Product	Version / Range
microsoft	windows_server_2025	to 10.0.26100.33158 (exc)
microsoft	windows_11_24h2	to 10.0.26100.8875 (exc)
microsoft	windows_11_26h1	to 10.0.28000.2525 (exc)
microsoft	windows_11_25h2	to 10.0.26200.8875 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-346	The product does not properly verify that the source of data or communication is valid.

Attack-Flow Graph

Executive Summary

This vulnerability is an origin validation error in Windows Network Address Translation (NAT). It allows an unauthorized attacker to perform spoofing over an adjacent network.

Detection Guidance

Detection of this vulnerability requires monitoring network traffic for spoofing attempts. Use network monitoring tools like Wireshark to inspect NAT traffic for anomalies. Check Windows Event Logs for unusual network activity. Ensure NAT rules are correctly configured and validate source IP addresses in incoming packets.

Impact Analysis

An attacker could exploit this to impersonate trusted systems or intercept network traffic, potentially leading to unauthorized access or data breaches.

Compliance Impact

This vulnerability could lead to data breaches or unauthorized access, which may violate compliance requirements for GDPR, HIPAA, or other regulations due to compromised data integrity and confidentiality.

Mitigation Strategies

Apply the latest security updates from Microsoft to address the origin validation error in Windows NAT. Monitor Microsoft's update guide for patches and install them promptly.

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