CVE-2025-27452: Endress MEAC300-FNADE4 Path Traversal Flaw

CVE-2025-27452 Overview

CVE-2025-27452 is an insecure configuration vulnerability affecting the Apache httpd webserver that serves the MEAC300-FNADE4 web application. The vulnerability stems from unnecessary Apache modules being activated that are not required for the FNADE4 web application's operation. These extraneous modules introduce security risks, most notably enabling directory listing functionality that can expose sensitive file and directory information to unauthorized actors.

Critical Impact

Attackers can remotely enumerate directory contents on affected MEAC300-FNADE4 devices without authentication, potentially exposing configuration files, firmware details, and internal application structure that could facilitate further attacks on industrial control systems.

Affected Products

• Endress MEAC300-FNADE4 Firmware (all versions)
• Endress MEAC300-FNADE4 Hardware

Discovery Timeline

• 2025-07-03 - CVE-2025-27452 published to NVD
• 2026-02-06 - Last updated in NVD database

Technical Details for CVE-2025-27452

Vulnerability Analysis

This vulnerability is classified under CWE-548 (Exposure of Information Through Directory Listing). The MEAC300-FNADE4 device ships with an Apache httpd webserver configuration that includes modules unnecessary for the device's intended web application functionality. When directory listing is enabled through these modules, any unauthenticated remote attacker with network access to the device can browse directory contents on the webserver.

The exposure is particularly concerning in industrial control system (ICS) environments where MEAC300-FNADE4 devices are typically deployed. Directory listing can reveal internal application structure, configuration file locations, firmware version information, and potentially sensitive operational data. This information disclosure could serve as reconnaissance for more sophisticated attacks against the industrial network.

Root Cause

The root cause is an insecure default configuration in the Apache httpd webserver bundled with the MEAC300-FNADE4 firmware. Specifically, Apache modules that enable directory indexing and listing functionality are activated despite not being required for the FNADE4 web application. This represents a failure to apply the principle of least functionality during firmware development and configuration.

Attack Vector

The vulnerability is exploitable remotely over the network without requiring authentication or user interaction. An attacker simply needs network connectivity to the MEAC300-FNADE4 device's web interface. By navigating to directories that lack an index file, the Apache webserver will automatically generate and serve a directory listing page, exposing file names, sizes, and modification dates to the attacker.

Directory listing attacks are trivial to execute—an attacker can use standard web browsers or automated tools like curl or wget to systematically enumerate accessible directories. The exposed information can include configuration files, backup files, log files, and other sensitive resources that developers may not have intended to be publicly accessible.

Detection Methods for CVE-2025-27452

Indicators of Compromise

• HTTP requests targeting directory paths without trailing file names (e.g., /admin/, /config/, /backup/)
• HTTP responses containing Apache autoindex module output (look for "Index of" in response body)
• Unusual volume of sequential directory enumeration requests from external IP addresses
• Access log entries showing 200 OK responses to directory paths that should return 403 Forbidden

Detection Strategies

• Monitor web server access logs for requests to known sensitive directories on MEAC300-FNADE4 devices
• Deploy network intrusion detection rules to identify Apache directory listing response patterns
• Implement anomaly detection for unusual browsing patterns against ICS device web interfaces
• Configure SIEM alerts for successful directory listing responses from industrial control devices

Monitoring Recommendations

• Enable verbose Apache access logging on MEAC300-FNADE4 devices if supported by firmware
• Deploy network traffic analysis tools at ICS network boundaries to detect reconnaissance activity
• Establish baseline normal traffic patterns to MEAC300-FNADE4 web interfaces for anomaly detection
• Review access logs regularly for evidence of directory enumeration attempts

How to Mitigate CVE-2025-27452

Immediate Actions Required

• Isolate affected MEAC300-FNADE4 devices from untrusted networks immediately
• Implement network segmentation to restrict access to device web interfaces to authorized personnel only
• Deploy firewall rules to block external access to MEAC300-FNADE4 web interfaces
• Review and follow CISA ICS Recommended Practices for industrial control system security

Patch Information

Consult the official vendor security advisory for firmware updates that address this vulnerability. SICK has published security advisories available through their Product Security Incident Response Team (PSIRT). Detailed vulnerability information is available in the SICK CSAF Advisory (PDF).

Contact Endress+Hauser support for specific remediation guidance and firmware update availability for MEAC300-FNADE4 devices.

Workarounds

• Disable unnecessary Apache modules, particularly mod_autoindex, if configuration access is available
• Configure Options -Indexes directive in Apache configuration to disable directory listing
• Deploy a reverse proxy or web application firewall (WAF) in front of affected devices to filter directory listing requests
• Implement access control lists (ACLs) to restrict web interface access to specific authorized IP addresses
• Place affected devices behind VPN infrastructure requiring authentication for access

If direct Apache configuration modification is possible on the device, disabling directory listing can be achieved through standard Apache configuration directives. However, given that this is embedded firmware, network-level mitigations may be the most practical approach until vendor patches are available.