CVE-2025-5871: SOL Connect Center Auth Bypass Flaw

CVE-2025-5871 Overview

CVE-2025-5871 is a missing authentication vulnerability [CWE-287] in Papendorf SOL Connect Center version 3.3.0.0. The flaw resides in an unspecified component of the product's Web Interface and allows remote attackers to interact with protected functionality without providing credentials. The issue has been publicly disclosed and exploit details are available. According to the disclosure, the vendor was contacted prior to public release but did not respond. SOL Connect Center is used to monitor and manage photovoltaic (solar) installations, making the exposed web interface an attractive target for reconnaissance against operational technology environments.

Critical Impact
Unauthenticated remote attackers can access web interface functionality intended to be restricted, enabling information disclosure from solar monitoring deployments exposed to untrusted networks.

Affected Products

Papendorf SOL Connect Center 3.3.0.0
Web Interface component of SOL Connect Center
Papendorf Software Engineering GmbH product line (SOL Connect Center)

Discovery Timeline

2025-06-09 - CVE-2025-5871 published to the National Vulnerability Database
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-5871

Vulnerability Analysis

The vulnerability is classified under [CWE-287] Improper Authentication. An attacker reaches functionality within the SOL Connect Center Web Interface without completing an authentication challenge. The attack is executed over the network, requires no privileges, and needs no user interaction. Based on the CVSS 4.0 vector, impact is limited to low confidentiality with no integrity or availability effects. This aligns with a scenario where an attacker retrieves data or configuration values exposed by the interface, rather than modifying the monitoring platform.

The exploit maturity is marked as proof-of-concept, indicating that working exploitation techniques have been publicly documented. The EPSS score of 0.414% reflects a low, but non-zero, near-term exploitation probability.

Root Cause

The root cause is missing authentication on one or more endpoints served by the Web Interface. Requests reach handler logic without a session check or credential validation, letting anonymous clients access resources that should require an authenticated user. Because the vendor did not respond to disclosure, the specific handler and route have not been formally documented by Papendorf.

Attack Vector

Exploitation is remote and unauthenticated. An attacker who can reach the SOL Connect Center management port over the network issues HTTP requests directly to the affected functionality. In deployments where the monitoring interface is reachable from the internet, or from any untrusted network segment, discovery is trivial with standard web reconnaissance tools. Refer to the GitHub CVE Request disclosure and VulDB entry #311630 for the public technical details.

Detection Methods for CVE-2025-5871

Indicators of Compromise

Unauthenticated HTTP GET or POST requests to SOL Connect Center Web Interface endpoints originating from external or unexpected internal source addresses.
Web server access logs showing responses with HTTP 200 status to protected paths without a preceding authentication request or valid session cookie.
Repeated crawling patterns against the 3.3.0.0 management interface from single source addresses.

Detection Strategies

Deploy web application firewall rules that require valid session tokens on all Web Interface paths and alert on anonymous access attempts.
Perform authenticated network scans to identify SOL Connect Center 3.3.0.0 instances exposed beyond intended management networks.
Correlate perimeter firewall logs with SOL Connect Center web logs to identify inbound access from non-management networks.

Monitoring Recommendations

Forward SOL Connect Center web server logs to a centralized log platform and build detections for high-volume unauthenticated requests.
Track baseline traffic volumes to the monitoring interface and alert on deviations that suggest scraping or enumeration.
Monitor egress from the SOL Connect Center host for unexpected outbound connections that could indicate follow-on activity.

How to Mitigate CVE-2025-5871

Immediate Actions Required

Remove SOL Connect Center 3.3.0.0 from any interface reachable from the internet or untrusted networks.
Restrict access to the Web Interface using network access control lists that permit only authorized management hosts.
Place the monitoring interface behind a VPN or reverse proxy that enforces authentication before requests reach the application.
Audit web server logs for prior unauthenticated access to determine whether reconnaissance has already occurred.

Patch Information

No vendor patch has been published. The disclosure notes that Papendorf Software Engineering GmbH did not respond to the researcher's outreach. Operators should track the VulDB entry for future vendor updates and contact Papendorf directly to request a fixed release.

Workarounds

Enforce authentication upstream by fronting the Web Interface with a reverse proxy such as nginx or Apache configured for HTTP Basic authentication or mutual TLS.
Segment the SOL Connect Center host into a dedicated OT management VLAN with strict east-west firewall rules.
Disable or firewall the Web Interface listener when active monitoring sessions are not required.
Require multi-factor authentication for all administrative access to the network segment hosting SOL Connect Center.

bash

# Example nginx reverse proxy enforcing authentication in front of SOL Connect Center
server {
    listen 443 ssl;
    server_name sol-connect.internal.example;

    ssl_certificate     /etc/nginx/certs/sol-connect.crt;
    ssl_certificate_key /etc/nginx/certs/sol-connect.key;

    # Restrict source networks to management subnet only
    allow 10.10.20.0/24;
    deny  all;

    location / {
        auth_basic           "SOL Connect Center - Authorized Personnel Only";
        auth_basic_user_file /etc/nginx/.htpasswd;

        proxy_pass         http://127.0.0.1:8080;
        proxy_set_header   Host $host;
        proxy_set_header   X-Real-IP $remote_addr;
    }
}