CVE-2026-42901: Microsoft Entra ID Privilege Escalation

CVE-2026-42901 Overview

CVE-2026-42901 is an origin validation error [CWE-346] in Microsoft Entra ID, Microsoft's cloud identity and access management service. The flaw allows an unauthenticated attacker to elevate privileges across a network without user interaction. Microsoft tracks the issue in its Security Update Guide and rates the vulnerability with a maximum CVSS 3.1 score of 10.0, reflecting a scope change that affects resources beyond the vulnerable component. Because Entra ID brokers authentication for Microsoft 365, Azure, and federated third-party applications, successful exploitation has direct consequences for tenant-wide identity trust boundaries.

Critical Impact

An unauthorized remote attacker can elevate privileges across Entra ID tenants, potentially compromising identities, tokens, and downstream cloud and SaaS resources that rely on Entra ID for authentication.

Affected Products

• Microsoft Entra ID (cloud service, identified by CPE cpe:2.3:a:microsoft:entra_id:-:*:*:*:*:*:*:*)
• Workloads and applications federated to Entra ID for authentication
• Microsoft 365 and Azure tenants relying on Entra ID identity tokens

Discovery Timeline

• 2026-05-22 - CVE-2026-42901 published to the National Vulnerability Database
• 2026-05-27 - Last updated in NVD database

Technical Details for CVE-2026-42901

Vulnerability Analysis

The vulnerability is classified as an origin validation error [CWE-346]. Microsoft Entra ID fails to correctly verify the origin of a request or token issuer during a network-facing authentication or authorization exchange. An attacker who can reach the affected service endpoint can submit crafted requests that the service treats as originating from a trusted source. Because Entra ID issues and validates security tokens used across the Microsoft cloud, an origin trust failure translates directly into a privilege elevation path. The scope-changed CVSS vector indicates impact extends beyond the directly vulnerable component to other identity-trusting resources.

Root Cause

The defect is the absence of, or improper enforcement of, validation logic that ties a request, message, or token to the legitimate origin Entra ID expects. CWE-346 weaknesses typically occur when a service relies on attacker-controlled headers, claims, or transport metadata to determine the source of a request. Microsoft has not published low-level technical details for CVE-2026-42901 beyond its advisory in the Security Update Guide.

Attack Vector

The attack vector is network-based, requires no privileges, and requires no user interaction. An unauthenticated attacker reaches an Entra ID endpoint over the network and sends a crafted request that the service incorrectly attributes to a trusted origin. Successful exploitation yields a higher-privileged identity context, enabling onward access to identities, applications, and data protected by Entra ID. No public proof-of-concept exploit, ExploitDB entry, or CISA KEV listing exists at publication. The current EPSS probability is low.

No verified exploit code is publicly available. Refer to the Microsoft CVE-2026-42901 Advisory for vendor-confirmed technical context.

Detection Methods for CVE-2026-42901

Indicators of Compromise

• Unexpected token issuance or sign-in events from Entra ID for high-privilege roles such as Global Administrator, Application Administrator, or Privileged Role Administrator.
• Authentication events with anomalous issuer, audience, or origin claims that do not match known tenant configuration.
• New service principals, application consent grants, or federation trust changes that were not initiated by a known administrator.

Detection Strategies

• Monitor Entra ID sign-in logs and audit logs for privilege elevation events, role assignment changes, and consent grants performed by unfamiliar identities.
• Correlate non-interactive sign-ins and token issuance with source IP, device, and application identifiers to surface origin anomalies.
• Alert on creation or modification of federated identity credentials, certificates, or trusted application registrations.

Monitoring Recommendations

• Stream Entra ID sign-in, audit, and provisioning logs into a SIEM or data lake for retention and cross-source correlation.
• Baseline normal administrative activity per role and tenant, and generate alerts on deviations.
• Continuously review Conditional Access policy changes and break-glass account usage.

How to Mitigate CVE-2026-42901

Immediate Actions Required

• Review the Microsoft CVE-2026-42901 Advisory and confirm tenant exposure status reported by Microsoft.
• Audit privileged role memberships, service principals, and application consent grants in Entra ID and revoke any that are not justified.
• Rotate credentials and certificates associated with high-value applications, federated identities, and break-glass accounts if suspicious activity is observed.

Patch Information

Microsoft Entra ID is a cloud-delivered service. Mitigations and fixes for CVE-2026-42901 are deployed by Microsoft on the service side rather than through customer-installed updates. Consult the Microsoft Security Update Guide entry for the authoritative remediation status and any tenant configuration steps required to fully address the issue.

Workarounds

• Enforce Conditional Access policies that require multi-factor authentication and compliant or hybrid-joined devices for all administrative access.
• Restrict administrative actions to Privileged Identity Management (PIM) with just-in-time activation, approval workflows, and short activation windows.
• Limit application and service principal permissions to the minimum required, and disable unused legacy authentication protocols at the tenant level.

# Configuration example: review high-privilege role assignments in Entra ID
# using Microsoft Graph PowerShell
Connect-MgGraph -Scopes "RoleManagement.Read.Directory","Directory.Read.All"
Get-MgDirectoryRole | ForEach-Object {
    $role = $_
    Get-MgDirectoryRoleMember -DirectoryRoleId $role.Id |
        Select-Object @{n='Role';e={$role.DisplayName}}, Id, AdditionalProperties
}