1. Introduction
The VMware Active Virtual Machines vulnerability allows enumeration of active virtual machines running on a vSphere server. This means someone with valid credentials could discover details about your VMs, potentially aiding in further attacks. Systems affected are typically those running the VMware vSphere platform. A successful exploit could lead to information disclosure impacting confidentiality.
2. Technical Explanation
- Root cause: The vSphere API does not sufficiently restrict access to virtual machine inventory information based on user roles and permissions.
- Exploit mechanism: An attacker authenticates to the vSphere server using valid credentials, then uses the API to query for a list of active VMs and their IP addresses.
- Scope: VMware vSphere versions are affected. Specific version ranges have not been identified in this report.
3. Detection and Assessment
You can check if your system is vulnerable by verifying the API endpoint responds with VM details when authenticated. A thorough method involves reviewing user permissions within vSphere.
- Quick checks: Log into the vSphere web client and confirm you can view a list of VMs under the ‘Virtual Machines’ inventory.
- Scanning: Nessus plugin ID 16829 is an example scanner detection method, but results should be verified manually.
- Logs and evidence: Review vSphere logs for API calls related to VM enumeration. Look for events indicating successful queries of the virtual machine inventory. Exact paths vary depending on your vSphere version and logging configuration.
# Example command placeholder:
# No specific command available, check via vSphere Web Client UI.
4. Solution / Remediation Steps
The following steps outline how to mitigate the risk of VM enumeration. These steps focus on limiting access and reducing potential impact.
4.1 Preparation
- Ensure you have valid credentials for rollback purposes. A roll back plan involves restoring from the pre-change snapshot.
- Changes should be performed during a scheduled maintenance window with appropriate approval.
4.2 Implementation
- Step 1: Review user roles and permissions within vSphere, ensuring least privilege is applied. Remove unnecessary access rights to VM inventory information.
- Step 2: If possible, restrict API access based on IP address or network segment.
- Step 3: Enable auditing of API calls related to virtual machine inventory.
4.3 Config or Code Example
Before
# Default role with full access to VM inventory.
# This is an example, actual configuration varies significantly.
role "Virtual Machine Administrator" {
permissions = ["*"]
}
After
# Modified role with restricted access to VM inventory.
# This is an example, actual configuration varies significantly.
role "Limited Virtual Machine Access" {
permissions = ["vm.guest_operations", "vm.power"] # Example limited permissions
}
4.4 Security Practices Relevant to This Vulnerability
Several security practices can help prevent this issue. Least privilege is key, as it limits the damage from compromised credentials. Input validation isn’t directly applicable here, but secure defaults in vSphere configuration are important.
- Practice 1: Implement least privilege to reduce the impact if an account with limited permissions is compromised.
- Practice 2: Regularly review user roles and permissions within vSphere to ensure they align with job functions.
4.5 Automation (Optional)
# No specific automation script provided due to complexity of vSphere configuration.
# PowerShell scripts can be used with the VMware PowerCLI module for managing roles and permissions, but require careful testing.
5. Verification / Validation
Confirm the fix by verifying that users with restricted permissions cannot enumerate VMs via the API. Test both through the UI and using a script.
- Post-fix check: Log in as a user with limited VM access and attempt to view the full VM inventory list. The operation should be denied or return an error message.
- Re-test: Re-run the initial detection method (vSphere Web Client UI) using the same limited user account. You should no longer see the full VM list.
- Smoke test: Verify that users with appropriate permissions can still perform their core tasks, such as powering on/off VMs and managing guest operating systems.
- Monitoring: Monitor vSphere logs for failed API calls related to VM enumeration attempts by restricted users.
# Post-fix command and expected output
# Attempting to list VMs with limited user: Error message indicating insufficient permissions.
6. Preventive Measures and Monitoring
Update your security baselines to include least privilege principles for vSphere access. Consider adding checks in your CI/CD pipeline to validate role configurations. A regular patch cycle is also important.
- Baselines: Update your VMware security baseline or CIS control implementation to enforce least privilege for all vSphere users and roles.
- Pipelines: Integrate static analysis tools into your deployment process to check for overly permissive role configurations in infrastructure-as-code templates.
- Asset and patch process: Implement a regular patch review cycle (e.g., monthly) to apply security updates to VMware vSphere components.
7. Risks, Side Effects, and Roll Back
- Risk or side effect 1: Incorrect permission settings may prevent authorized users from performing necessary tasks. Mitigation: Thorough testing in a non-production environment.
- Risk or side effect 2: API access restrictions could impact automated workflows that rely on VM inventory information. Mitigation: Carefully review and update any affected scripts or applications.
- Roll back: Restore the vSphere environment from the pre-change snapshot or backup. Verify user permissions are returned to their original state.
8. References and Resources
- Vendor advisory or bulletin: VMware Security Advisories
- NVD or CVE entry: No specific CVE currently assigned for this enumeration issue.
- Product or platform documentation relevant to the fix: VMware vSphere Documentation