Introduction
In my recent analysis of Identity and Access Management (IAM) controls within Azure Cloud environments, I identified a significant risk related to improper role assignments. Specifically, the use of broad built-in roles, such as Owner and Contributor, without granular permission management can lead to unrestricted access. Although the tested environment contained a limited number of accounts, this misconfiguration represents a substantial security risk that can compromise cloud infrastructure and sensitive data. This article thoroughly explores the issue, potential impacts, and recommended corrective measures.
Nature of the Vulnerability
Azure Cloud Shell provides a convenient interface that allows users to interact directly with Azure APIs through Bash or PowerShell in a web browser. When users initiate Cloud Shell for the first time, they are prompted to create a Storage Account automatically prefixed with “cs”. This account persists user files, scripts, and configurations across sessions. However, because role assignments within Azure subscriptions are not sufficiently restrictive, roles such as Contributor grant excessive permissions.
A user holding the Contributor role can browse and modify any Storage Account within the subscription, including those automatically created by administrators using Cloud Shell. This configuration oversight allows users to view or insert files into another user’s Storage Account. In practical terms, a Contributor-level user could manipulate scripts or commands in an administrator’s Storage Account. When the administrator unknowingly executes this altered content in their next Cloud Shell session, the malicious commands run with administrative privileges. Consequently, the attacker can gain full control over critical infrastructure or elevate their permissions even further.
Proof of Concept
During testing, I identified two user accounts with the Contributor role. These accounts did not possess administrative privileges, yet they retained full access to all Storage Accounts. To confirm the vulnerability, I reviewed Storage Accounts marked by the prefix “cs”, indicating automatic creation through Azure Cloud Shell.
In particular, I observed the Storage Account named “cs-name-usr”, which clearly belonged to a subscription administrator actively using Azure Cloud Shell. Stored scripts and configurations were evident within this account. Given the permissions granted to the Contributor accounts, I demonstrated that it was possible to access and modify these files without any restriction. I could also read sensitive information stored within the files or inject malicious commands, which would then be executed during subsequent administrator sessions.
This scenario highlights the importance of privilege management. An attacker exploiting this misconfiguration in environments could elevate their permissions from a Contributor-level user to an Owner-level account. Such elevation provides complete control over cloud resources, including the ability to alter infrastructure components, access sensitive data, or compromise the integrity and availability of business-critical applications.
Impact and Risk Analysis
The security implications of this vulnerability are severe. Because Cloud Shell is commonly used by administrators to perform quick, direct management actions on cloud resources, the risk of unauthorized modification to their environment is high. Without granular access control, attackers can easily leverage Contributor-level privileges to target high-privilege accounts.
The risk is further amplified in multi-user environments where multiple accounts regularly utilize Azure Cloud Shell. In such scenarios, distinguishing legitimate from malicious activity becomes challenging, increasing the probability of successful privilege escalation and subsequent attacks.
Recommended Mitigations
To address and mitigate this vulnerability effectively, a more granular and customized approach to role management in Azure Cloud environments is essential. Instead of relying on built-in roles such as Owner or Contributor, administrators should define and assign custom roles that strictly adhere to the principle of least privilege, granting only the permissions necessary for each user’s tasks.
Custom roles reduce the risk of unauthorized access to resources, limiting potential damage even if user accounts become compromised. Additionally, administrators should implement rigorous monitoring and auditing of user activities in Cloud Shell and associated Storage Accounts to detect and respond quickly to suspicious actions.
Finally, extending these practices beyond user accounts to include application and service accounts is equally important. Every entity interacting with Azure resources should have appropriately defined permissions, reinforcing comprehensive security throughout the cloud environment.
Conclusion
The discovery of this IAM-related vulnerability underscores the importance of proper access control and permission management in cloud infrastructure. Failure to apply a granular, least-privilege approach can lead to significant risks, including unauthorized privilege escalation. Implementing the recommended corrective measures will substantially improve the security posture, minimizing the possibility of successful privilege-escalation attacks in Azure Cloud environments.
