How to remediate – UPnP API Listing

1. Introduction

The UPnP API Listing vulnerability means a remote server is making its Universal Plug and Play (UPnP) service control protocol document XML available. This allows attackers to discover services running on the device and potentially interact with them. Businesses should be aware as it can expose internal network information and lead to unauthorised access or control of devices, particularly those without strong security measures. Confidentiality, integrity, and availability may all be affected if exploited successfully.

2. Technical Explanation

The vulnerability occurs because the remote device supports a SOAP API over UPnP and Nessus can retrieve its Service Control Protocol Document XML. An attacker can use this information to understand the available services and attempt to exploit them. There is no specific CVE currently associated with simply listing the API, but exploitation of the exposed APIs may have associated CVEs. A realistic example would be an attacker discovering a vulnerable media server service through UPnP and using it to gain access to files on the network.

• Root cause: The device exposes a UPnP SCPD XML file without sufficient restriction.
• Exploit mechanism: An attacker queries the UPnP endpoint, retrieves the XML document, parses it for available services, and attempts to exploit vulnerabilities in those services using SOAP requests.
• Scope: Devices implementing UPnP are affected, including routers, network attached storage (NAS) devices, media servers, and smart home hubs.

3. Detection and Assessment

You can confirm a system is vulnerable by checking for the exposed UPnP service. A thorough method involves using a vulnerability scanner to identify the specific services offered through UPnP.

• Quick checks: Use nmap -sU --script upnp-info to check if UPnP is enabled and responding on the target device.
• Scanning: Nessus vulnerability ID 10853 can detect this issue, as well as other potential UPnP vulnerabilities.
• Logs and evidence: Check application logs for UPnP-related activity or SOAP requests originating from external sources.

nmap -sU --script upnp-info 192.168.1.100

4. Solution / Remediation Steps

The following steps detail how to fix the issue by disabling or restricting UPnP access.

4.1 Preparation

• Ensure you have administrator credentials to access the device’s settings. A roll back plan involves restoring from the pre-change snapshot.
• A change window may be needed depending on the criticality of the affected service and potential impact of disabling UPnP. Approval from a senior IT team member is recommended.

4.2 Implementation

1. Step 1: Log in to the device’s web interface as an administrator.
2. Step 2: Navigate to the UPnP settings section (usually found under Network, Advanced Settings, or Security).
3. Step 3: Disable UPnP if possible. If disabling is not an option, restrict access to trusted IP addresses only.
4. Step 4: Save the changes and reboot the device if prompted.

4.3 Config or Code Example

Before

UPnP: Enabled

After

UPnP: Disabled

4.4 Security Practices Relevant to This Vulnerability

Several security practices can help prevent this issue.

• Practice 1: Least privilege – limit the services exposed on a network and restrict access to only those that are necessary.
• Practice 2: Safe defaults – ensure UPnP is disabled by default, requiring explicit configuration to enable it.

4.5 Automation (Optional)

No automation script is provided as the steps vary significantly between devices.

5. Verification / Validation

Confirm the fix worked by checking that UPnP is no longer accessible from outside the network.

• Post-fix check: Run nmap -sU --script upnp-info again and verify that no UPnP services are listed.
• Re-test: Re-run the Nessus scan (ID 10853) to confirm the vulnerability is no longer detected.
• Monitoring: Monitor network traffic for unexpected UPnP-related activity or SOAP requests originating from external sources.

nmap -sU --script upnp-info 192.168.1.100

6. Preventive Measures and Monitoring

Update security baselines to include disabling UPnP by default.

• Baselines: Update your network device baseline or policy to require UPnP to be disabled unless specifically needed, as per CIS controls.
• Pipelines: Include checks in CI/CD pipelines for insecure configurations during deployment of new devices.
• Asset and patch process: Review the configuration of all network devices regularly (e.g., quarterly) to ensure compliance with security policies.

7. Risks, Side Effects, and Roll Back

Disabling UPnP may break functionality that relies on it, such as automatic port forwarding for gaming or media streaming.

• Risk or side effect 1: Disabling UPnP might require manual configuration of port forwarding rules for some applications.
• Roll back: Step 1: Log in to the device’s web interface. Step 2: Navigate to the UPnP settings section. Step 3: Re-enable UPnP and save the changes. Step 4: Reboot the device if prompted.

8. References and Resources

Links to sources that match this exact vulnerability.

• Vendor advisory or bulletin: Check your device manufacturer’s website for specific UPnP security advisories.
• NVD or CVE entry: No specific CVE is associated with simply listing the API, but search NVD for vulnerabilities related to exposed UPnP services.
• Product or platform documentation relevant to the fix: Refer to your device’s manual for instructions on disabling or configuring UPnP.