AZ_ASSIGN_ROLES

Summary

Forestall ACL Alias	AZ_ASSIGN_ROLES
Azure Alias	Assign Roles (Role Assignment Write)
Affected Object Types	Subscriptions, Management Groups, Resource Groups, Resources
Exploitation Certainty	Certain
Custom Role Action	Microsoft.Authorization/roleAssignments/write - create, update, or delete role assignments

Built-in Roles:

• Owner (8e3af657-a8ff-443c-a75c-2fe8c4bcb635)
• User Access Administrator (18d7d88d-d35e-4fb5-a5c3-7773c20a72d9)
• Role Based Access Control Administrator (f58310d9-a9f6-439a-9e8d-f62e7b41a168)
• Reservations Administrator (a8889054-8d42-49c9-bc1c-52486c10e7cd)

Description

AZ_ASSIGN_ROLES represents the ability to create, modify, or delete Azure RBAC role assignments. This is one of the most dangerous permissions in Azure because it enables direct privilege escalation.

A principal with Microsoft.Authorization/roleAssignments/write at a given scope can:

• Grant themselves Owner - assign themselves or a controlled identity the Owner role.
• Grant any role to any principal - create role assignments for users, groups, service principals, or managed identities.
• Enable lateral movement - assign roles to other compromised identities.
• Establish persistence - create hidden role assignments that survive credential rotation.

The ability to assign roles is explicitly excluded from the Contributor role, making it the key differentiator between Contributor and Owner.

Role	Has roleAssignments/write
Owner	Yes
Contributor	No
User Access Administrator	Yes
Role Based Access Control Administrator	Yes

Identification

PowerShell (Az Module)Azure CLIAzure Portal

PowerShell (Az Module)

Connect-AzAccount

# List role assignments for roles that grant roleAssignments/write
$dangerousRoles = @(
    "Owner",
    "User Access Administrator",
    "Role Based Access Control Administrator"
)

Get-AzRoleAssignment |
    Where-Object { $dangerousRoles -contains $_.RoleDefinitionName } |
    Select-Object DisplayName, SignInName, RoleDefinitionName, Scope |
    Sort-Object RoleDefinitionName, Scope |
    Format-Table -AutoSize

# Check custom roles for roleAssignments/write
Get-AzRoleDefinition -Custom | Where-Object {
    $_.Actions -contains "*" -or
    $_.Actions -contains "Microsoft.Authorization/*" -or
    $_.Actions -contains "Microsoft.Authorization/roleAssignments/*" -or
    $_.Actions -contains "Microsoft.Authorization/roleAssignments/write"
} | Select-Object Name, @{N="Actions";E={$_.Actions -join ", "}}

Azure CLI

# List Owner and User Access Administrator assignments
az role assignment list --query "[?roleDefinitionName=='Owner' || roleDefinitionName=='User Access Administrator']" -o table

# Check custom roles for dangerous permissions (checks all permissions, not just first)
az role definition list --custom-role-only true --query "[?permissions[?contains(actions, 'Microsoft.Authorization/roleAssignments/write')]]"

Azure Portal

1. Open Azure Portal -> Subscriptions (or target scope).
2. Go to Access control (IAM) -> Role assignments.
3. Filter by Role = Owner or Role = User Access Administrator.
4. Review all principals listed - these can assign roles.

Exploitation

Self-Elevation to Owner

Connect-AzAccount

$userId = "<userId>"

# Assign Owner role to yourself at subscription scope
New-AzRoleAssignment -ObjectId $userId -RoleDefinitionName "Owner" -Scope "/subscriptions/<subid>"

# Verify the assignment
Get-AzRoleAssignment -ObjectId $userId |
    Where-Object { $_.RoleDefinitionName -eq "Owner" } |
    Format-Table -AutoSize

Self-elevate to Owner with PowerShell role assignment

Assign Owner to a Service Principal for Persistence

Connect-AzAccount

# Create a role assignment for a service principal
$spnObjectId = "<ServicePrincipalObjectId>"
New-AzRoleAssignment -ObjectId $spnObjectId -RoleDefinitionName "Owner" -Scope "/subscriptions/<SubscriptionId>"

Assign Owner to a service principal with PowerShell

Azure CLI

# Self-elevate to Owner
az role assignment create --assignee "<YourObjectId>" --role "Owner" --scope "/subscriptions/<SubscriptionId>"

# Assign Owner to another principal
az role assignment create --assignee "<TargetObjectId>" --role "Owner" --scope "/subscriptions/<SubscriptionId>"

Assign Owner with Azure CLI

Mitigation

1. Minimize principals with role assignment capability

   • Remove Owner and User Access Administrator from identities that don’t strictly need them.
   • Use Contributor where full resource management is needed but role assignment is not.

2. Use Privileged Identity Management (PIM)

   • Configure eligible (not permanent) assignments for Owner and User Access Administrator.
   • Require approval and MFA for activation.
   • Set short activation windows.

3. Apply conditions to role assignments

   • Use Azure ABAC (Attribute-Based Access Control) to constrain what roles can be assigned.
   • The Role Based Access Control Administrator role supports conditions by default.

4. Use Azure Policy

   • Create policies to audit or deny role assignments to specific principals or at broad scopes.

5. Enable alerts

   • Configure alerts for Microsoft.Authorization/roleAssignments/write operations.

Detection

Use the Azure Portal:

1. Open Azure Portal -> Monitor -> Activity Log.
2. Filter by Operation name = Create role assignment or Delete role assignment.
3. Review the Caller and Target Resource to identify who made role assignment changes and what was assigned.
4. For subscription-level view: Go to Subscriptions -> select subscription -> Activity log -> filter for Microsoft.Authorization/roleAssignments/write.

References

• https://learn.microsoft.com/en-us/azure/role-based-access-control/role-assignments-portal
• https://learn.microsoft.com/en-us/azure/role-based-access-control/built-in-roles#owner
• https://learn.microsoft.com/en-us/azure/role-based-access-control/built-in-roles#user-access-administrator
• https://learn.microsoft.com/en-us/azure/role-based-access-control/conditions-overview