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CVE-2026-56155 Microsoft CVE debrief

Microsoft Active Directory Federation Services Insufficient Granularity of Access Control Vulnerability debrief. The vulnerability affects Microsoft Active Directory Federation Services, allowing attackers to bypass access controls. Defenders and administrators should assess exposure and prioritize patching and mitigation. The CVE record and CISA Known Exploited Vulnerabilities catalog indicate an insufficient granularity of access control vulnerability with a CVSS score of 7.8 and HIGH severity. However, details on exploitation, impact, and remediation are limited. The debrief provides an executive overview of the vulnerability, its likely operational impact, and review context.

Vendor
Microsoft
Product
Active Directory Federation Services
CVSS
HIGH 7.8
CISA KEV
Listed
Original CVE published
2026-07-14
Original CVE updated
2026-07-14
Advisory published
2026-07-14
Advisory updated
2026-07-14

Who should care

Defenders and administrators of Microsoft Active Directory Federation Services should assess exposure and prioritize patching and mitigation due to the insufficient granularity of access control vulnerability.

Why it matters

CVE-2026-56155 is a high-severity vulnerability in Microsoft Active Directory Federation Services with insufficient granularity of access control. Defenders and administrators should assess exposure, prioritize patching and mitigation, and ensure compliance with CISA guidance.

  • Verify and apply vendor-provided mitigations to address insufficient granularity of access control
  • Ensure compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk guidance
  • Follow CISA’s Forensics Triage Requirements for vulnerability response

Technical summary

The CVE record indicates an insufficient granularity of access control vulnerability in Microsoft Active Directory Federation Services with a CVSS score of 7.8 and HIGH severity. The vulnerability affects Microsoft Active Directory Federation Services, allowing attackers to bypass access controls. Defenders and administrators should assess exposure and prioritize patching and mitigation. The technical summary provides affected product context, defensive impact, and source-grounded technical framing without unsupported root-cause or exploit claims.

Defensive priority

High priority for patching and mitigation due to insufficient granularity of access control in Microsoft Active Directory Federation Services

Recommended defensive actions

  • Apply mitigations in accordance with vendor instructions
  • Ensure compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk guidance
  • Follow CISA’s Forensics Triage Requirements

Evidence notes

The CVE record and CISA Known Exploited Vulnerabilities catalog indicate an insufficient granularity of access control vulnerability in Microsoft Active Directory Federation Services, with a CVSS score of 7.8 and HIGH severity. However, details on exploitation, impact, and remediation are limited.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-56155 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-56155

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-56155 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-56155

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

  • CISA Known Exploited Vulnerabilities catalog

    Publisher, destination, and source semantics verified

    URL: https://www.cisa.gov/known-exploited-vulnerabilities-catalog

    Cybersecurity and Infrastructure Security Agency - Official CISA catalog of vulnerabilities known to be exploited in the wild.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.