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Known exploited vulnerability

CVE-2026-56155

highCVSS 3.1 7.8In CISA KEVEPSS 0.35%Published · Microsoft

The short answer

CVE-2026-56155 affects Microsoft Windows 10 Version 1607 and is rated high (CVSS 7.8). CISA added it to the Known Exploited Vulnerabilities catalog on 2026-07-14: attackers are using it, so patch it first.

What it is

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

Weakness: CWE-1220.

Severity

7.8 high

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Exploited (CISA KEV)

Yes, since Jul 14, 2026

Federal due date Jul 28, 2026

EPSS, next 30 days

0.35%

Higher than 28% of scored CVEs

How it can be exploited

Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

What CISA says to do

Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for…

Affected products

Windows 10 Version 1607, Windows 10 Version 1809, Windows Server 2012, Windows Server 2012 (Server Core installation), Windows Server 2012 R2, Windows Server 2012 R2 (Server Core installation), Windows Server 2016, Windows Server 2016 (Server Core installation), Windows Server 2019, Windows Server 2019 (Server Core installation), Windows Server 2022, Windows Server 2025. NVD's record lists the exact affected versions.

References

Questions

Is CVE-2026-56155 being exploited?

Yes. CISA added CVE-2026-56155 to its Known Exploited Vulnerabilities catalog on 2026-07-14, with a federal remediation due date of 2026-07-28.

How do I fix CVE-2026-56155?

CISA's required action: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for…

From NVD, CISA KEV, FIRST EPSS and OSV.dev, checked . Status on NVD: Analyzed. The description is NVD's text, quoted as published.

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