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Review reviewHigh

CVE-2026-56181

Microsoft Windows 11 Version 24H2, Windows 11 Version 25H2, Windows 11 version 26H1

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

CVSS
8.3
EPSS
0.24%
15.4% percentile
CISA KEV
Not listed
Published
2026.07.15
PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV
Exploit probability0.24%
Technical severityCVSS 8.3

Vulnerability overview

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

Affected product and versions

Product
Microsoft Windows 11 Version 24H2, Windows 11 Version 25H2, Windows 11 version 26H1
Affected versions
>= 10.0.26100.0 < 10.0.26100.8875, >= 10.0.26200.0 < 10.0.26200.8875, >= 10.0.28000.0 < 10.0.28000.2525, >= 10.0.26100.0 < 10.0.26100.33158, < 10.0.26100.8875, < 10.0.26200.8875, < 10.0.28000.2525, < 10.0.26100.33158
Fixed versions
10.0.26100.8875, 10.0.26200.8875, 10.0.28000.2525, 10.0.26100.33158

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide
  1. 1
    Identify

    Confirm that Microsoft Windows 11 Version 24H2, Windows 11 Version 25H2, Windows 11 version 26H1 and an affected version are present.

  2. 2
    Prioritize

    Combine exploitation signals with asset exposure and business criticality.

  3. 3
    Remediate

    Follow the vendor advisory or supported update path and preserve rollback options.

  4. 4
    Verify

    Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector
CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
CWE
CWE-346
CVE-2026-56181 — Microsoft Windows 11 Version 24H2, Windows 11 Version 25H2, Windows 11 version 26H1 | SECUFOCUS NOW