EUVD-2026-44042
GHSA-p436-qch3-9m59
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Requires an existing low-privilege local session on the AD FS host (AV:L, PR:L) with no user interaction, and successful escalation yields full high impact on the same system.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Lifecycle Timeline
3DescriptionCVE.org
Insufficient granularity of access control in Active Directory Federation Services (AD FS) allows an authorized attacker to elevate privileges locally.
AnalysisAI
Local privilege escalation in Microsoft Active Directory Federation Services (AD FS) lets an already-authenticated low-privileged user on the host gain higher privileges due to insufficient granularity of access control (CWE-1220). Affected deployments span AD FS on Windows Server 2012 through Windows Server 2025, and the flaw carries a CVSS 7.8 with high confidentiality, integrity, and availability impact. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires the attacker to already be a low-privileged authenticated principal with local access to a host running the AD FS role (CVSS AV:L, PR:L, UI:N), so this is not remotely reachable and cannot be triggered by an anonymous network attacker. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS vector (AV:L/AC:L/PR:L/UI:N/S:U, C:H/I:H/A:H) describes a locally-exploitable, low-complexity flaw requiring a low-privilege authenticated foothold and no user interaction, yielding full impact within the same security scope - consistent with a classic privilege-escalation primitive rather than a remote entry point. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker who has already obtained a low-privileged authenticated session on an AD FS server - for example a compromised service account or a foothold from another local flaw - invokes the affected AD FS functionality whose access control is enforced too coarsely and thereby elevates to higher privileges on the identity server. Given AV:L/AC:L, the technique is reliable and requires no user interaction, but there is no public exploit identified at time of analysis, so an adversary would need to develop the primitive themselves. |
| Remediation | Patch available per vendor advisory: apply the Microsoft security update for CVE-2026-56155 to all AD FS servers across the affected Windows Server builds via the Microsoft Update Guide at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-56155 (no exact fix build number was provided in the input, so pull the KB matching each server's OS version from that page). … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, inventory all AD FS deployments across Windows Server 2012-2025 environments and assess current access control configurations. …
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