Guests are not assigned high privileged directory roles

Overview

When guest users are assigned highly privileged directory roles such as Global Administrator or Privileged Role Administrator, organizations create significant security vulnerabilities that threat actors can exploit for initial access through compromised external accounts or business partner environments. Since guest users originate from external organizations without direct control of security policies, threat actors who compromise these external identities can gain privileged access to the target organization’s Microsoft Entra tenant.

When threat actors obtain access through compromised guest accounts with elevated privileges, they can escalate their own privilege to create other backdoor accounts, modify security policies, or assign themselves permanent roles within the organization. The compromised privileged guest accounts enable threat actors to establish persistence and then make all the changes they need to remain undetected. For example they could create cloud-only accounts, bypass Conditional Access policies applied to internal users, and maintain access even after the guest’s home organization detects the compromise. Threat actors can then conduct lateral movement using administrative privileges to access sensitive resources, modify audit settings, or disable security monitoring across the entire tenant. Threat actors can reach complete compromise of the organization’s identity infrastructure while maintaining plausible deniability through the external guest account origin.

Remediation

• Remove Guest users from privileged roles

Run it

The check runs as part of the whole assessment, with the ZeroTrustAssessment module installed:

Install-Module ZeroTrustAssessment -Scope CurrentUser
Connect-Maester
Invoke-Maester -Pack ZTA -SkipBuiltIn

Leave out -SkipBuiltIn to run Maester’s own checks in the same run.

About this check

Severity	High
Effort to fix	Medium
Impact on users	Low
Pillar	Identity
Category	Application management
Product	Entra ID
Feature	Roles and administrators
Area	Privileged access
ATT&CK	T1078.004 Cloud Accounts, T1199 Trusted Relationship
Licence	Free
Tenant	Workforce, External

Product, feature, area and ATT&CK are Maester’s: the assessment does not record them, so Maester keeps them in the pack’s taxonomy.json.

A Microsoft check, part of the Zero Trust Assessment pack. Text from ZeroTrustAssessment 3.1.0, © Microsoft, MIT licence.