Affects Microsoft Windows NAT — widely used OS networking component; can enable network spoofing and lateral movement impacting enterprise infrastructure.
CVE-2026-56179
Windows NAT origin validation flaw allows adjacent-network spoofing.
Is CVE-2026-56179 being exploited?
Not confirmed. CVE-2026-56179 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.23% probability of exploitation in the next 30 days.
How severe is CVE-2026-56179?
CVE-2026-56179 is rated High with a CVSS score of 8.3. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-56179?
Yes. A fix has been recorded for CVE-2026-56179. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-56179 affect?
CVE-2026-56179 affects Microsoft Windows (NAT component), Windows Server (with NAT enabled), Windows client (with NAT enabled). Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-56179?
Apply vendor patch when released; restrict adjacent-network access and monitor NAT traffic.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Adjacent-network attacker can spoof packets/hosts via Windows NAT origin validation flaw, enabling bypass of filters, MITM, or lateral movement.
Patch when possible
- affected>= 10.0.26100.0 and < 10.0.26100.9168
- affected>= 10.0.26200.0 and < 10.0.26200.9168
- affected>= 10.0.28000.0 and < 10.0.28000.2704
- affected>= 10.0.26100.0 and < 10.0.26100.33296
- affected>= 10.0.26100.0 and < 10.0.26100.33296
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.