How to remediate – SnortReport nmap.php target Parameter Arbitrary Command Execution

1. Introduction

SnortReport nmap.php target Parameter Arbitrary Command Execution is a vulnerability in the SnortReport add-on module for Snort, allowing remote attackers to run commands on the web server. This poses a high risk as it could lead to complete system compromise. Systems running vulnerable versions of SnortReport are affected. Successful exploitation can result in loss of confidentiality, integrity and availability of the host system.

2. Technical Explanation

• Exploit mechanism: An attacker sends a crafted HTTP request to nmap.php with a malicious payload within the target parameter, causing arbitrary commands to be executed. For example, sending ?target=whoami will execute the ‘whoami’ command on the server.
• Scope: SnortReport add-on module for Snort. Specific affected versions are not detailed in available information.

3. Detection and Assessment

Confirming vulnerability requires checking if the vulnerable script exists and is accessible, then attempting to inject a command. A thorough method involves testing with various payloads.

• Quick checks: Check for the existence of the nmap.php file within the SnortReport installation directory via your web server’s document root.
• Scanning: Nessus plugin ID 68931 may identify this vulnerability, but results should be verified manually.
• Logs and evidence: Web server access logs may show requests to nmap.php with suspicious ‘target’ parameters. Look for unusual characters or commands in the URL.

ls -l /path/to/snortreport/nmap.php

4. Solution / Remediation Steps

Currently, a specific solution is not available. The following steps outline general best practices to mitigate risk until an official patch is released.

4.1 Preparation

• Ensure you have access to restore the backup in case of issues. A roll back plan is to restore the original files from the backup.
• A change window may be required depending on your environment and risk tolerance. Approval from a senior administrator may be necessary.

4.2 Implementation

1. Step 1: Restrict access to the nmap.php script using web server configuration (e.g., .htaccess, nginx config). This prevents direct access to the vulnerable file.
2. Step 2: Implement a Web Application Firewall (WAF) rule to block requests containing suspicious characters or commands in the ‘target’ parameter.
3. Step 3: Monitor web server logs for any attempts to access nmap.php and investigate immediately.

4.3 Config or Code Example

Before

# No access restrictions on nmap.php

After

<Files nmap.php>
  Require all denied
</Files>

4.4 Security Practices Relevant to This Vulnerability

Several security practices can help prevent this type of vulnerability. Input validation is crucial, as is the principle of least privilege.

• Practice 1: Least privilege reduces the impact if an attacker gains command execution. Run web server processes with minimal necessary permissions.

4.5 Automation (Optional)

Automation is not directly applicable without a patch, but WAF rules can be deployed via automation tools.

# Example ModSecurity rule (adjust as needed for your environment)
SecRule REQUEST_URI "/snortreport/nmap.php" "id:900100,phase:2,deny,log,msg:'SnortReport nmap.php access blocked'"

5. Verification / Validation

Confirm the fix by attempting to access nmap.php and verifying that it is blocked or does not execute commands.

• Post-fix check: Attempt to access http://yourserver/snortreport/nmap.php?target=whoami. The expected output should be an error message (e.g., 403 Forbidden).
• Re-test: Repeat the initial detection attempt, and confirm that it no longer succeeds in executing commands.
• Monitoring: Monitor web server logs for blocked requests to nmap.php. An alert could be set if any attempts are detected.

curl -I http://yourserver/snortreport/nmap.php?target=whoami

6. Preventive Measures and Monitoring

Regular security baselines and vulnerability scanning can help prevent similar issues. Incorporating checks into your CI/CD pipeline is also beneficial.

• Baselines: Update a web server security baseline to include restrictions on sensitive scripts like nmap.php.
• Asset and patch process: Implement a regular patch review cycle for all software, including add-on modules like SnortReport.

7. Risks, Side Effects, and Roll Back

• Risk or side effect 1: Blocking access to nmap.php may prevent legitimate users from using it.
• Risk or side effect 2: WAF rules can sometimes cause false positives, blocking valid traffic.
• Roll back: Remove the web server configuration changes (e.g., .htaccess rule) and disable any WAF rules that were added. Restore the original nmap.php file from backup if necessary.

8. References and Resources

• Vendor advisory or bulletin: http://twitter.com/hdmoore/statuses/22630926839