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CVE-2026-56155.

Severity, exploit probability and exploitation status for one vulnerability, drawn from NVD, FIRST EPSS and CISA's exploited catalogue.

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known exploited Microsoft Active Directory Federation Services Insufficient Granularity of Access Control Vulnerability

Vendor / product: Microsoft - Active Directory Federation Services
Listed by CISA: 2026-07-14
Federal fix deadline: 2026-07-28 (passed)
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 evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.

Scores

CVSS 3.1: 7.8 high CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS: 2.3% estimated probability of exploitation in the next 30 days (higher than 82% of all CVEs)
Weakness class: CWE-1220

ATT&CK techniques

inferred from weakness class no curated mapping exists for this CVE; these are the techniques typically seen with CWE-1220 vulnerabilities

ReconnaissanceResource DevelopmentInitial AccessExecutionPersistencePrivilege EscalationStealthDefense ImpairmentCredential AccessDiscoveryLateral MovementCollectionCommand and ControlExfiltrationImpact

T1574 Hijack Execution Flow

ExecutionStealth

Adversaries may execute their own malicious payloads by hijacking the way operating systems run programs.

via sub-technique T1574.010 Services File Permissions Weakness

Inferred from CWE-1220.

T1574 on attack.mitre.org

See these techniques on the full ATT&CK matrix.

Description

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

Published: 2026-07-14
Last modified: 2026-07-15
NVD status: Analyzed

References

Covered in Decrypted

The AD FS zero-day hiding inside a record Patch Tuesday (2026-07-15)

CVSS measures how bad exploitation would be; EPSS estimates how likely exploitation is within 30 days; the CISA listing means it is already happening. Read them together: a CVSS 9.8 with EPSS 0.04% is usually less urgent than a CVSS 7.2 on the exploited list. Data: NVD, FIRST EPSS, CISA KEV; detail is cached for a week, scores for a day. ATT&CK techniques come from the CTID KEV mappings project where a curated mapping exists, otherwise they are inferred from the weakness class and labelled as such. ATT&CK is a registered trademark of The MITRE Corporation. © 2026 The MITRE Corporation. This work is reproduced and distributed with the permission of The MITRE Corporation.