How to remediate – UPnP Client Detection

1. Introduction

The UPnP Client Detection vulnerability means this machine is responding to Universal Plug and Play (UPnP) network requests. UPnP allows devices on a network to discover each other automatically, simplifying connections but also creating a potential attack surface. This affects many operating systems and embedded devices. A successful exploit could allow remote attackers to control the device. Impact on confidentiality, integrity, and availability is possible depending on the specific services exposed through UPnP.

2. Technical Explanation

This machine answered a unicast UPnP NOTIFY packet by attempting to retrieve an XML description advertised by Nessus. This indicates that the UPnP client service is active and responding to requests from external sources. An attacker could use this to map network services, potentially leading to further exploitation. There is no specific CVE associated with simply *having* a UPnP client enabled; the risk lies in what services are exposed through it.

• Root cause: The UPnP client service is running and configured to respond to external requests.
• Exploit mechanism: An attacker sends a UPnP request, which prompts the device to reveal information about its network configuration and available services. This information can then be used to launch targeted attacks. For example, an attacker could discover exposed ports and attempt to exploit vulnerabilities on those services.
• Scope: Windows, macOS, Linux systems with UPnP client software enabled are affected. Embedded devices like routers and smart home hubs are also commonly vulnerable.

3. Detection and Assessment

Confirming a system is vulnerable involves checking if the UPnP service is running and responding to requests. A quick check can be done via command line, while thorough assessment requires network scanning.

• Quick checks: On Windows, use `net start | find “UPnP”` in Command Prompt. If the service is running, it will appear in the output.
• Scanning: Nessus vulnerability ID 10429 can detect UPnP client exposure. Other scanners may have similar signatures.
• Logs and evidence: Windows Event Logs may contain events related to UPnP activity under “Microsoft-Windows/UPnP/Operational”.

net start | find "UPnP"

4. Solution / Remediation Steps

The best solution is usually to disable the UPnP client service if it’s not required. If needed, restrict access and regularly review exposed services.

4.1 Preparation

• Dependencies: Ensure no critical network functionality relies on UPnP. Roll back plan: re-enable the service if issues occur.
• Change window: A standard maintenance window is recommended, with approval from IT management.

4.2 Implementation

1. Step 1: Stop the “UPnP Device Host” service in Windows Services (services.msc).
2. Step 2: Set the startup type for “UPnP Device Host” to “Disabled”.

4.3 Config or Code Example

Before

sc queryex UPnPDeviceHost

After

sc config UPnPDeviceHost start= disabled

4.4 Security Practices Relevant to This Vulnerability

Several security practices can help mitigate this vulnerability type.

• Practice 1: Least privilege – disable unnecessary services like UPnP to reduce the attack surface.
• Practice 2: Safe defaults – configure systems with the most secure settings by default, disabling features that are not essential.

4.5 Automation (Optional)

A PowerShell script can automate the service disablement process.

# Stop and disable UPnP Device Host service
Stop-Service -Name "UPnPDeviceHost" -Force
Set-Service -Name "UPnPDeviceHost" -StartupType Disabled

5. Verification / Validation

Confirm the fix by checking if the UPnP service is stopped and disabled, then re-running the initial detection method.

• Post-fix check: Run `net start | find “UPnP”` in Command Prompt. No output should be displayed.
• Re-test: Re-run the Nessus scan (ID 10429). The vulnerability should no longer be reported.
• Smoke test: Verify basic network connectivity remains functional, such as pinging external websites.
• Monitoring: Monitor Windows Event Logs for any unexpected UPnP related events.

net start | find "UPnP"

6. Preventive Measures and Monitoring

Update security baselines to include disabling unnecessary services, and incorporate checks in deployment pipelines.

• Baselines: Include a setting to disable UPnP in your standard OS baseline or CIS control implementation.
• Pipelines: Add a check during system build or configuration management to ensure the UPnP service is disabled.
• Asset and patch process: Review exposed services regularly as part of vulnerability management.

7. Risks, Side Effects, and Roll Back

Disabling UPnP may break functionality in some applications that rely on it. A roll back involves re-enabling the service.

• Roll back: Step 1: Set the startup type for “UPnP Device Host” to “Automatic”. Step 2: Start the “UPnP Device Host” service in Windows Services (services.msc).

8. References and Resources

Links only to sources that match this exact vulnerability.

• Vendor advisory or bulletin: No specific vendor advisory exists for simply having UPnP enabled, but consult your OS documentation.
• NVD or CVE entry: No specific CVE exists for simply having UPnP enabled.
• Product or platform documentation relevant to the fix: Microsoft’s UPnP Documentation