Is CVE-2026-56155 being actively exploited?

Yes. CVE-2026-56155 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, added on July 14, 2026.

What is the CVSS score for CVE-2026-56155?

CVE-2026-56155 has a CVSS 3.1 base score of 7.8 (HIGH).

CVE-2026-56155

HIGH · CVSS 7.8CISA KEV: actively exploitedEPSS 0.3%EU EUVD: exploited

Insufficient granularity of access control in Active Directory Federation Services (AD FS) allows an authorized attacker to elevate privileges locally.

Key facts

CVSS score: 7.8 (v3.1)
Severity: HIGH
CVSS vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Weakness (CWE): CWE-1220
EPSS score: 0.3% (26th percentile)
In CISA KEV: Yes, added July 14, 2026
In EU EUVD: Yes (EUVD-2026-44042)
Published: July 14, 2026
NVD last modified: July 15, 2026
Status: Analyzed

CISA Known Exploited Vulnerability

Microsoft Active Directory Federation Services Insufficient Granularity of Access Control Vulnerability

Added to the KEV catalog on July 14, 2026; federal remediation due July 28, 2026.

EU Vulnerability Database (EUVD)

This vulnerability is also tracked by ENISA as EUVD-2026-44042 in the EU Vulnerability Database. ENISA flags it as known exploited. Last updated in EUVD on October 8, 2026.

View on the EU Vulnerability Database

Affected products

microsoft / windows 10 1607
microsoft / windows 10 1607
microsoft / windows 10 1809
microsoft / windows 10 1809
microsoft / windows server 2012
microsoft / windows server 2012
microsoft / windows server 2016
microsoft / windows server 2019
microsoft / windows server 2022
microsoft / windows server 2025

Certified products that may be affected

1 FIPS 140 or Common Criteria certified product, from automated matching by sec-certs.org.

Microsoft Windows 10 and Server version 1903 (May 2019 Update) - Microsoft Corporation - Common Criteria 2019-22-INF-2839 - archived

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-56155(Vendor Advisory)
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-56155(US Government Resource)

Last updated September 17, 2026 · Source: NVD, CISA KEV, FIRST.org EPSS

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