How to remediate – AppSocket & socketAPI Printers – Do Not Scan

1. Introduction

The remote host appears to be an AppSocket or socketAPI printer and will not be scanned. This vulnerability means that port 9100 is intentionally skipped during scans, reducing the overall coverage of security assessments. This typically affects network printers using these protocols. A successful scan attempt would likely waste paper but poses no direct risk to confidentiality, integrity, or availability.

2. Technical Explanation

The host identifies as an AppSocket or socketAPI printer, triggering a bypass in the scanning process. This is not an exploitable vulnerability itself, but rather a configuration that prevents full assessment. There are no known CVEs associated with this identification; it’s a deliberate scan exclusion mechanism. An attacker could potentially hide malicious services on port 9100 if they can configure the printer to appear as one of these types. Affected systems include printers running AppSocket or socketAPI firmware.

• Root cause: The scanner identifies the host as an AppSocket or socketAPI printer.
• Exploit mechanism: An attacker could run a service on port 9100 that is not scanned, potentially bypassing security checks.
• Scope: Printers using AppSocket and socketAPI protocols.

3. Detection and Assessment

Confirming whether a system is identified as an AppSocket or socketAPI printer can be done through network discovery tools or by checking the device’s configuration interface. Scanning tools will typically log this exclusion.

• Quick checks: Use nmap -p 9100 and check if the scan skips port 9100 with a message indicating it’s a printer.
• Scanning: Nessus or other vulnerability scanners may report this as an information finding, noting the skipped port.
• Logs and evidence: Review scanner logs for messages related to AppSocket or socketAPI printers.

nmap -p 9100 192.168.1.100
Starting Nmap 7.92 ( https://nmap.org ) at 2023-10-27 14:00 BST
Nmap scan report for 192.168.1.100
Host is up (0.00021s latency).
Not shown: 999 closed ports
PORT     STATE SERVICE
9100/tcp filtered printer
Nmap done: 1 IP address (1 host up) scanned in 0.15 seconds

4. Solution / Remediation Steps

Since this is a deliberate scan exclusion, the “remediation” involves understanding why it’s happening and whether full scanning is required. If the printer does not handle sensitive data or run critical services on port 9100, no action may be needed. However, if security requires complete coverage, consider alternative scanning methods or reconfiguring the printer (if possible).

4.1 Preparation

• Backups are generally not required for this assessment. No services need to be stopped unless you plan to reconfigure the printer.
• Dependencies: Access to the printer’s configuration interface may be needed. Roll back involves reverting any changes made to the printer’s settings.
• Change window needs and approvals depend on your organization’s policies.

4.2 Implementation

1. Step 1: Determine if full scanning of port 9100 is necessary based on risk assessment.
2. Step 2: If required, investigate the printer’s configuration options for scan exclusion settings.
3. Step 3: Disable any scan exclusion features if possible and re-run the scan.

4.3 Config or Code Example

Before

# Assume printer config has an option like this:
scan_exclusion = true 

After

# Change the setting in the printer's configuration to:
scan_exclusion = false 

4.4 Security Practices Relevant to This Vulnerability

• Asset inventory: Knowing all devices on your network, including printers, is crucial for security assessments.
• Network segmentation: Isolating printers from critical systems can limit the impact of potential vulnerabilities.

4.5 Automation (Optional)

Automation is unlikely to be suitable for this specific issue as it requires manual configuration changes on each printer.

5. Verification / Validation

• Post-fix check: Run nmap -p 9100 and confirm that the port is no longer filtered or skipped.
• Re-test: Re-run your vulnerability scan and verify that port 9100 is included in the results.
• Smoke test: Print a test page to ensure basic printer functionality is working as expected.

nmap -p 9100 192.168.1.100
Starting Nmap 7.92 ( https://nmap.org ) at 2023-10-27 14:15 BST
Nmap scan report for 192.168.1.100
Host is up (0.00018s latency).
Not shown: 999 closed ports
PORT     STATE SERVICE
9100/tcp open  printer
Nmap done: 1 IP address (1 host up) scanned in 0.14 seconds

6. Preventive Measures and Monitoring

• Baselines: Include printer configurations in your security baseline to ensure consistent settings.
• Asset and patch process: Regularly review the asset inventory for new or changed devices, including printers.

7. Risks, Side Effects, and Roll Back

• Risk or side effect 1: Changing printer configuration could disrupt printing services if not done carefully.
• Roll back: Revert any changes made to the printer’s configuration settings.

8. References and Resources

• IAVB: 0001-B-0525