Summary
Impact: Spoofing. Microsoft rating: Moderate. Not known to be exploited — Exploitation Less Likely. Customer action: Required.
Details
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.
Security updates
10.0.26100.33158 — https://support.microsoft.com/help/5099536
10.0.26200.8875 — https://support.microsoft.com/help/5101650
10.0.28000.2525 — https://support.microsoft.com/help/5101649
Vulnerabilities 1
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High 8.3
Windows Network Address Translation (NAT) Spoofing Vulnerability
Origin validation error in Windows Network Address Translation (NAT) allows an unauthorized attacker to perform spoofing over an adjacent network.
Revision history
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#1
Information published.
References
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CVE-2026-56181 Windows Network Address Translation (NAT) Spoofing Vulnerability - HTML
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-56181
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Microsoft Exploitability Index
https://www.microsoft.com/en-us/msrc/exploitability-index?rtc=1
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Microsoft Support Lifecycle
https://support.microsoft.com/lifecycle
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Common Vulnerability Scoring System
https://www.first.org/cvss