What is CVE-2026-56181?
Origin validation error in Windows Network Address Translation (NAT) allows an unauthorized attacker to perform spoofing over an adjacent network.
The record classifies CVE-2026-56181 under weakness class CWE-346. Its CVSS v3 base vector states that the flaw is reachable from an adjacent network, needs no prior authentication, needs no user interaction, and has high impact on confidentiality, integrity, availability. 5 affected-product entries are recorded, across 1 vendor, listed below. The identifier was first published 106 days ago.
Severity and exploitation probability
- CVSS v3.1 base score
- 8.3 — HIGH
CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H/E:U/RL:O/RC:C - EPSS (FIRST)
- 0.2% probability of exploitation in the next 30 days, higher than 14.7% of all scored CVEs
- CISA KEV
- Not listed in the CISA Known Exploited Vulnerabilities catalog
- Threadlinqs priority
- 4.7/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- Published
- 2026-07-14, last modified 2026-08-06
Is CVE-2026-56181 being exploited?
No public exploitation evidence for CVE-2026-56181 is recorded in the sources Threadlinqs tracks — CISA KEV, Exploit-DB, public proof-of-concept repositories and ProjectDiscovery Nuclei — as of 2026-08-06. That is an absence of evidence in those feeds, not a guarantee that the vulnerability is unexploited.
Affected products and versions
- Microsoft: Windows 11 Version 24H2, Windows 11 Version 25H2, Windows 11 version 26H1, Windows Server 2025, Windows Server 2025 (Server Core installation)
How to fix CVE-2026-56181
The record marks a vendor fix as available for CVE-2026-56181. Patch reference: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-56181. Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-56181. Apply the vendor fix referenced above to every affected product listed in this record, then confirm the running version against the vendor advisory.
Threat activity tracking CVE-2026-56181
1 tracked threat in the Threadlinqs corpus references CVE-2026-56181, either in the campaign’s CVE list or as an indicator on the campaign record.
Sources
Enriched from CVE.org, NVD, FIRST EPSS, GitHub Security Advisories. Last verified by Threadlinqs on . This product uses the NVD API but is not endorsed or certified by the NVD.