EUVD-2026-56763
GHSA-rxw5-jh43-59h9
Severity by source
AV:A/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
Adjacent-only reach (AV:A), high complexity for state-aware spoofing (AC:H), no credentials needed (PR:N), scope change as NAT failure affects downstream hosts (S:C).
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
3DescriptionCVE.org
Origin validation error in Windows Network Address Translation (NAT) allows an unauthorized attacker to perform spoofing over an adjacent network.
AnalysisAI
Spoofing via origin validation failure in Windows Network Address Translation (NAT) exposes Windows Server 2025 and Windows 11 (versions 24H2 through 26H1) to network-layer address spoofing by unauthenticated attackers on an adjacent network. The flaw, rooted in CWE-346, allows crafted packets to bypass NAT's origin-trust enforcement, potentially enabling man-in-the-middle interception or manipulation of traffic transiting the NAT boundary. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires the attacker to be physically or logically adjacent to the target - i.e., on the same LAN, VLAN, Wi-Fi segment, or directly connected network where the vulnerable Windows host is reachable at Layer 2 or Layer 3 with no intervening routing hop. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The NVD CVSS score of 8.3 (AV:A/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H) accurately characterizes a high-severity vulnerability with meaningful architectural constraints. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Apply the vendor-released security update from Microsoft that brings affected builds to or above the fixed thresholds: Windows Server 2025 to build 10.0.26100.33296 or later, Windows 11 24H2 and 25H2 to build 10.0.26100.9168 or later, and Windows 11 26H1 to build 10.0.28000.2704 or later. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, identify and inventory all Windows Server 2025 and Windows 11 systems (versions 24H2 through 26H1) performing NAT functions in your environment and isolate them from untrusted adjacent networks if patches cannot be applied immediately. …
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Same weakness CWE-346 – Origin Validation Error
View allSame technique Authentication Bypass
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External POC / Exploit Code
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