1. Introduction
The VMware vCenter Inactive Virtual Machines vulnerability allows an attacker with valid credentials for a VMware vCenter server to list virtual machines that are currently powered off. This information could assist in reconnaissance activities, potentially leading to further attacks on the wider network. Affected systems are typically VMware vCenter servers running any version where inactive VMs can be enumerated. A successful exploit has a low impact on confidentiality but minimal impact on integrity or availability.
2. Technical Explanation
The vulnerability occurs because VMware vCenter does not sufficiently restrict access to information about all virtual machines, including those that are powered off. An attacker with legitimate login credentials can query the server and retrieve details of inactive VMs. There is no known CVE associated with this specific enumeration issue. An example attack would involve an attacker logging into a vCenter instance and using the API or UI to list all VMs, identifying those in a powered-off state for potential targeting.
- Root cause: Insufficient access control on virtual machine metadata within VMware vCenter.
- Exploit mechanism: An authenticated user queries the vCenter server via its API or web interface to retrieve details of all VMs, including those that are inactive.
- Scope: VMware vCenter servers across various versions are potentially affected if they allow enumeration of inactive virtual machines.
3. Detection and Assessment
To confirm vulnerability, first check the vCenter server version. Then attempt to list all VMs via the UI or API. Look for evidence of inactive VMs being returned in the results.
- Quick checks: Check the vCenter Server version through the web interface (Adminstration > About).
- Scanning: Nessus plugin ID 16879 may identify this issue as an information disclosure vulnerability. This is provided as an example only.
- Logs and evidence: Review vCenter logs for API calls related to VM listing or enumeration. Specific log paths vary depending on the vCenter version.
# No specific command available, assessment relies on UI/API access and observation of results.4. Solution / Remediation Steps
The primary remediation is to limit access to VMware vCenter and regularly review user permissions. There are no direct patches for this enumeration issue; the focus is on reducing exposure.
4.1 Preparation
- Ensure you have valid credentials for rollback in case of issues. A roll back plan is to restore from the pre-change snapshot.
- Changes should be made during a scheduled maintenance window with appropriate approval from IT management.
4.2 Implementation
- Step 1: Review all user accounts and groups that have access to vCenter Server.
- Step 2: Remove unnecessary permissions, granting only the minimum required access for each role.
- Step 3: Implement multi-factor authentication (MFA) where possible.
- Step 4: Regularly audit user permissions and activity logs.
4.3 Config or Code Example
Before
#Example: User 'admin' has full administrative access.
#This is insecure as it allows unrestricted VM enumeration.After
#Example: User 'admin' has limited role-based access, restricting VM enumeration.
#Ensure the user only has permissions required for their job function.4.4 Security Practices Relevant to This Vulnerability
List only practices that directly address this vulnerability type. Use neutral wording and examples instead of fixed advice. For example: least privilege, input validation, safe defaults, secure headers, patch cadence. If a practice does not apply, do not include it.
- Practice 1: Least privilege access to reduce the impact if an account is compromised.
- Practice 2: Regular user and permission reviews to identify and remove unnecessary access rights.
4.5 Automation (Optional)
# No specific automation script available for this enumeration issue. Focus on manual permission reviews and access control configuration.5. Verification / Validation
- Post-fix check: Log in as a limited user and attempt to list VMs via the UI or API. Expect only authorized VMs to be returned.
- Re-test: Re-run the initial assessment (UI/API access) with the limited user account. Verify that inactive VMs are not listed.
- Smoke test: Ensure core vCenter functionality, such as VM power on/off and console access, remains operational for authorized users.
- Monitoring: Review vCenter logs for unusual API calls or permission-related events.
# No specific command available; verification relies on UI/API observation of results with limited user accounts.6. Preventive Measures and Monitoring
Suggest only measures that are relevant to the vulnerability type. Use “for example” to keep advice conditional, not prescriptive.
- Baselines: Update security baselines or policies to enforce least privilege access control for VMware vCenter.
- Pipelines: Incorporate permission review checks into CI/CD pipelines where applicable.
- Asset and patch process: Maintain a regular schedule for reviewing user permissions and activity logs within vCenter Server.
7. Risks, Side Effects, and Roll Back
- Risk or side effect 2: Unexpected service impacts are possible, though unlikely. Mitigation is restoring from the pre-change snapshot.
- Roll back: Restore the vCenter VM from the pre-change snapshot if any issues occur.
8. References and Resources
- Vendor advisory or bulletin: VMware Security Advisories
- NVD or CVE entry: No specific CVE is associated with this enumeration issue.
- Product or platform documentation relevant to the fix: VMware vSphere Documentation