Restless Guests: The Hidden Entra Risk That Could Compromise Your Cloud

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It starts with something most organisations see as low-risk a guest account invited into your Microsoft Entra environment.

But that invitation could open the door to a hidden, high-risk attack path you didn’t even know existed.

🧠 The Unexpected Attack Surface

Researchers have discovered a little-known flaw in how Microsoft Entra handles subscriptions and billing roles. It allows a guest user to create and transfer subscriptions into your tenant while retaining full ownership of them.

Here’s how it works:

  • Guest is invited into your Entra ID tenant
  • They use their own billing role from their home tenant to create a subscription
  • They transfer that subscription into your tenant
  • Now they’re the owner inside your environment

And most Azure admins have no visibility of this via standard Entra permission reviews.

🔓 What Can a Guest Do with Subscription Access?

Once inside, a “restless guest” can:

  • Access and expose high-privilege account info
  • Modify or disable Azure security policies
  • Create persistent user-managed identities
  • Register fake compliant devices to bypass conditional access

This isn’t hypothetical. It’s already being exploited in the wild — and it’s often completely off the security radar.

💡 Why Most Security Teams Miss This

Most Azure teams focus on Entra Directory Roles and Azure RBAC Roles. But this attack uses billing account permissions, which live outside the usual access control perimeter.

Plus, by default, any user even a guest can invite others. A compromised user could invite an attacker with the right permissions and bypass your defences completely.

✅ Mitigations You Can Apply Now

  • 🛑 Block guest-created subscriptions: Use Microsoft’s Subscription Policy settings
  • 👤 Audit all guest users and remove those no longer needed
  • 🔒 Harden guest permissions and disable guest-to-guest invites
  • 🕵️‍♂️ Monitor all subscriptions for unknown guest-created resources
  • 📱 Check conditional access and device compliance rules

🔍 Final Word

The idea that “guests don’t pose a serious risk” no longer holds. If you use Microsoft Entra especially in a B2B scenario it’s time to rethink guest access and billing visibility.

💬 Have you reviewed your Entra guest policies recently?

👉 Need help spotting hidden attack paths? Follow TheCyberGuyAU for straight-talk security insights.

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