Description

BeyondTrust researchers have identified a critical vulnerability in Microsoft Entra ID and Azure environments that enables attackers to escalate privileges using lesser-known billing roles. This threat arises from a loophole in cross-tenant collaboration, where guest users—often granted limited access—can exploit billing roles to gain elevated permissions in external Azure tenants. The core issue lies in Microsoft’s billing permission model under Enterprise Agreements (EA) and Microsoft Customer Agreements (MCA). Roles such as Billing Account Owner or Azure Subscription Creator, when assigned in the attacker’s home tenant, can be misused to create or move Azure subscriptions into a target tenant where they are only guests. These subscriptions then grant the attacker Owner rights—bypassing the expected restrictions for guest accounts. Microsoft has confirmed this behavior is “by design,” aimed at facilitating collaboration, but the lack of opt-in control presents a serious risk. BeyondTrust demonstrated that even a free Azure trial tenant can be used to initiate such attacks. Once a malicious subscription is established, attackers can identify privileged users, create persistent identities, manipulate security policies, and exploit conditional access rules—all while appearing as legitimate guests. To mitigate this risk, organizations should enforce strict subscription policies, audit guest user activity, and monitor for suspicious subscription creation. Tools like BeyondTrust Identity Security Insights can aid in identifying these hidden threats. This vulnerability highlights the urgent need to revisit guest access policies in Entra ID and Azure—before attackers take full advantage of this silent backdoor.