CVE-2026-56181

Windows Network Address Translation (NAT) Spoofing Vulnerability

HIGH

8.3

CVSS Score

Published: July 14, 2026 at 05:10 PM UTC

Updated: October 28, 2026 at 08:06 PM UTC

4 products affected across 1 vendorWindows Server 2025Windows 11 24H2Windows 11 25H2

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Severity

HIGH8.3

Exploit prediction

EPSS 0.3%

SSVC

No known exploit

Description

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

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Windows 11 24H2 · Microsoft

95%

v < 10.0.26100.887510.0.26100.0

Affected range stops below 10.0.26100.8875, so it looks safe — our inference, not a vendor statement

Windows 11 25H2 · Microsoft

95%

v < 10.0.26200.887510.0.26200.0

Affected range stops below 10.0.26200.8875, so it looks safe — our inference, not a vendor statement

Windows 11 26H1 · Microsoft

95%

v < 10.0.28000.252510.0.28000.0

Affected range stops below 10.0.28000.2525, so it looks safe — our inference, not a vendor statement

Windows Server 2025 · Microsoft

95%

v < 10.0.26100.3315810.0.26100.0

Affected range stops below 10.0.26100.33158, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-56181

References (1)

Vendor AdvisoryPatch

Source: cverecord

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-56181

SSVC — Action Prioritization

SSVCNo known exploitNot automatableTotal impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

8.3HIGH[email protected]

Attack Vector: ADJACENT_NETWORK
Complexity: HIGH
Privileges: NONE
User Interaction: NONE
Scope: CHANGED
Confidentiality: HIGH
Integrity: HIGH
Availability: HIGH

Vector?

Quick Info

StatusANALYZED

CWE

CWE-346

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