CVE-2026-25951: FUXA Path Traversal Vulnerability

CVE-2026-25951 Overview

CVE-2026-25951 is a path traversal vulnerability affecting FUXA, a web-based Process Visualization (SCADA/HMI/Dashboard) software. Prior to version 1.2.11, a flaw in the path sanitization logic allows an authenticated attacker with administrative privileges to bypass directory traversal protections. By using nested traversal sequences (e.g., ....//), an attacker can write arbitrary files to the server filesystem, including sensitive directories like runtime/scripts. This leads to Remote Code Execution (RCE) when the server reloads the malicious scripts.

Critical Impact

Authenticated attackers with administrative access can achieve full Remote Code Execution on FUXA servers through arbitrary file write capabilities, potentially compromising critical SCADA/HMI infrastructure.

Affected Products

• FUXA versions prior to 1.2.11
• Web-based SCADA/HMI/Dashboard deployments using vulnerable FUXA installations
• Industrial Process Visualization systems running unpatched FUXA software

Discovery Timeline

• 2026-02-09 - CVE-2026-25951 published to NVD
• 2026-02-10 - Last updated in NVD database

Technical Details for CVE-2026-25951

Vulnerability Analysis

This vulnerability stems from inadequate path sanitization in FUXA's file handling mechanisms. The application implements directory traversal protections, but the filtering logic fails to account for nested traversal sequences. When an attacker supplies a path containing ....// patterns, the sanitization routine removes the first ../ occurrence, leaving behind a valid ../ sequence that bypasses the protection. This allows authenticated administrators to write files to arbitrary locations on the server filesystem.

The attack becomes particularly dangerous when combined with FUXA's script execution capabilities. By writing malicious content to the runtime/scripts directory, an attacker can achieve code execution when the server processes or reloads these scripts. Given FUXA's role in SCADA/HMI environments, successful exploitation could lead to compromise of critical industrial control systems.

Root Cause

The root cause is classified as CWE-22 (Improper Limitation of a Pathname to a Restricted Directory - Path Traversal). The path sanitization implementation uses a naive filtering approach that only processes traversal sequences in a single pass. This allows attackers to craft nested sequences where the removal of one traversal component reveals another valid traversal sequence, effectively bypassing the intended security controls.

Attack Vector

The attack is network-based and requires authenticated access with administrative privileges. An attacker would craft HTTP requests containing nested directory traversal sequences in file path parameters. The malformed path would pass through the flawed sanitization logic, allowing the attacker to specify arbitrary file write locations. The typical attack flow involves:

1. Authenticating to FUXA with administrative credentials
2. Crafting a file write request with nested traversal sequences (e.g., ....//....//runtime/scripts/malicious.js)
3. Writing malicious script content to the target directory
4. Triggering script reload or waiting for automatic reprocessing
5. Achieving code execution on the underlying server

The vulnerability affects the file write functionality where user-supplied paths are processed without adequate recursive sanitization.

Detection Methods for CVE-2026-25951

Indicators of Compromise

• Unexpected files appearing in the runtime/scripts directory or other sensitive server locations
• HTTP requests containing nested traversal patterns such as ....//, ..../\, or similar encoded variants
• Unusual file write operations from the FUXA web application process
• New or modified scripts in FUXA runtime directories with suspicious content

Detection Strategies

• Monitor web application logs for requests containing path traversal patterns including nested sequences like ....// or URL-encoded equivalents
• Implement file integrity monitoring on FUXA installation directories, particularly runtime/scripts
• Deploy web application firewall rules to detect and block nested directory traversal attempts
• Analyze authentication logs for unusual administrative access patterns preceding file operations

Monitoring Recommendations

• Enable verbose logging for file system operations performed by the FUXA application
• Configure alerts for any file creation or modification events in critical FUXA directories
• Monitor network traffic for suspicious POST requests to FUXA endpoints that handle file operations
• Review administrative session activity for anomalous behavior patterns

How to Mitigate CVE-2026-25951

Immediate Actions Required

• Upgrade FUXA to version 1.2.11 or later immediately to address the vulnerability
• Audit administrative accounts and review access logs for any suspicious file write operations
• Implement network segmentation to limit access to FUXA administrative interfaces
• Review the runtime/scripts directory for any unauthorized or suspicious files

Patch Information

The vulnerability is fixed in FUXA version 1.2.11. The patch addresses the path sanitization flaw by implementing proper recursive filtering of directory traversal sequences. Organizations should upgrade to this version or later to remediate the vulnerability.

For detailed patch information, refer to the GitHub Commit Update and the GitHub Release v1.2.11. Additional security information is available in the GitHub Security Advisory GHSA-68m5-5w2h.

Workarounds

• Restrict network access to FUXA administrative interfaces using firewall rules or network segmentation
• Implement additional authentication controls such as multi-factor authentication for administrative accounts
• Deploy a web application firewall (WAF) configured to block path traversal patterns in requests
• Consider running FUXA in a containerized environment with restricted filesystem access

# Example: Restrict filesystem permissions on FUXA runtime directories
chmod 750 /path/to/fuxa/runtime/scripts
chown root:fuxa /path/to/fuxa/runtime/scripts

# Example: Configure firewall to limit access to FUXA admin interface
iptables -A INPUT -p tcp --dport 1881 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 1881 -j DROP