1. Introduction
The Untangle NG Firewall Captive Portal RCE vulnerability allows a remote attacker to execute code on affected systems. This is due to insufficient authentication checks when handling file uploads within the Captive Portal module. Successful exploitation could lead to complete system compromise, impacting confidentiality, integrity and availability of network services. Systems running the Untangle NG Firewall with the Captive Portal module enabled are typically affected.
2. Technical Explanation
- Root cause: Missing authentication checks prior to handling file uploads in the Captive Portal module.
- Exploit mechanism: An attacker sends a crafted HTTP POST request containing a malicious file to the Captive Portal endpoint, then accesses it via an HTTP GET request triggering execution.
- Scope: Untangle NG Firewall systems with the Captive Portal module enabled are affected. Specific versions have not been publicly detailed.
3. Detection and Assessment
Confirming vulnerability requires checking if the Captive Portal module is active. A thorough assessment involves reviewing server logs for suspicious file uploads.
- Quick checks: Check the Untangle NG Firewall web interface under ‘Captive Portal’ to see if the module is enabled.
- Scanning: Nessus plugin ID 16829 may identify this vulnerability, but results should be verified manually.
- Logs and evidence: Examine /var/log/untangle/capture.log for unusual file uploads or access attempts.
# Example command placeholder:
# No specific command available to directly confirm exposure without interface access.
4. Solution / Remediation Steps
The recommended solution is to remove the Captive Portal module, as no patch is currently available.
4.1 Preparation
- Stopping services is not required for this remediation. Roll back involves re-enabling the Captive Portal module from the web interface, restoring from backup if necessary.
- Change windows are recommended to minimise disruption. Approval may be needed depending on your organisation’s policies.
4.2 Implementation
- Step 1: Log in to the Untangle NG Firewall web interface as an administrator.
- Step 2: Navigate to ‘Apps’ then select ‘Captive Portal’.
- Step 3: Disable and remove the Captive Portal module.
4.3 Config or Code Example
Before
# Captive Portal module is enabled in the Untangle NG Firewall web interface.
After
# Captive Portal module is disabled and removed from the Untangle NG Firewall web interface.
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.
- Practice 1: Least privilege – limiting the permissions granted to applications reduces the impact if they are compromised.
- Practice 2: Input validation – rigorously checking all user-supplied data prevents malicious code from being processed.
4.5 Automation (Optional)
# No automation is currently available for this remediation due to the lack of an API endpoint for module removal.
5. Verification / Validation
Confirm the fix by verifying that the Captive Portal module has been removed and attempting to access its functionality.
- Post-fix check: Check the Untangle NG Firewall web interface under ‘Apps’. The Captive Portal module should no longer be listed.
- Re-test: Attempting to access the Captive Portal URL should result in an error or redirect, confirming it is disabled.
- Smoke test: Verify other network services (firewall rules, VPN connections) continue to function as expected.
# Post-fix command and expected output
# No specific command available; verify via web interface.
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 your Untangle NG Firewall security baseline to reflect the removal of non-essential modules like Captive Portal.
- Pipelines: Implement a regular review process for enabled applications and their associated risks.
- Asset and patch process: Maintain a current inventory of all installed software and promptly address identified vulnerabilities.
7. Risks, Side Effects, and Roll Back
- Risk or side effect 1: Removing Captive Portal will disable any associated network access features.
- Risk or side effect 2: Users relying on Captive Portal for authentication may experience service disruption.
- Roll back: Log in to the Untangle NG Firewall web interface, navigate to ‘Apps’, and re-enable the Captive Portal module. Restore from backup if necessary.
8. References and Resources
- Vendor advisory or bulletin: https://blogs.securiteam.com/index.php/archives/2724
- NVD or CVE entry: No CVE currently assigned.
- Product or platform documentation relevant to the fix: https://untangle.com/documentation/