CVE-2026-13207: FUXA Authentication Bypass Vulnerability

CVE-2026-13207 Overview

CVE-2026-13207 is an authentication bypass vulnerability in FUXA versions 1.3.1 and prior. The REST API router fails to normalize dot-segment sequences before applying authentication middleware. Unauthenticated attackers can access protected endpoints by prefixing paths with dot-segments such as /api/./users, /api/./roles, and /api/project/../users. The malformed paths bypass authentication checks while still resolving to sensitive backend handlers. Successful exploitation returns user and role data without credentials. The flaw is tracked under CWE-290: Authentication Bypass by Spoofing and was published in CISA ICS Advisory ICSA-26-181-02.

Critical Impact
Remote unauthenticated attackers can retrieve user accounts, roles, and other sensitive data from FUXA REST API endpoints over the network.

Affected Products

FUXA version 1.3.1
FUXA versions prior to 1.3.1
FUXA REST API router component

Discovery Timeline

2026-06-30 - CVE-2026-13207 published to NVD
2026-07-01 - Last updated in NVD database

Technical Details for CVE-2026-13207

Vulnerability Analysis

FUXA is an open-source, web-based process visualization and SCADA/HMI application used in industrial control system (ICS) environments. The REST API exposes endpoints for managing users, roles, projects, and runtime configuration. Authentication is enforced by middleware that inspects the request path and applies protection before routing to handlers.

The vulnerability stems from a mismatch between path handling in the authentication middleware and the downstream router. The middleware evaluates the raw request path literally, treating a URI containing dot-segments as distinct from its canonical form. The router later resolves dot-segments and dispatches the request to the intended handler. This inconsistency allows attackers to reach protected handlers without ever satisfying the authentication check.

An attacker sends an HTTP request with dot-segments prefixed to a protected route, for example GET /api/./users or GET /api/project/../users. The middleware does not recognize the transformed path as a protected route and forwards the request. The handler then returns user accounts, role assignments, and other configuration data.

Root Cause

The root cause is missing URI normalization prior to authorization enforcement, categorized as CWE-290: Authentication Bypass by Spoofing. The API layer trusts unnormalized input for access control decisions while relying on the router to canonicalize the same input for dispatch. Any additional path-manipulation primitives, such as URL-encoded slashes or repeated separators, may expand the bypass surface further.

Attack Vector

Exploitation requires only network access to the FUXA HTTP interface and no credentials or user interaction. An attacker issues a crafted GET request against endpoints such as /api/./users, /api/./roles, or /api/project/../users. The response returns JSON data belonging to protected resources. Exposed FUXA deployments reachable from the internet or from lateral positions inside OT networks are directly at risk. For technical remediation details, refer to the CISA ICS Advisory ICSA-26-181-02 and the FUXA release notes.

Detection Methods for CVE-2026-13207

Indicators of Compromise

HTTP requests to FUXA containing dot-segment patterns such as /./, /../, or URL-encoded equivalents (%2e%2f, %2e%2e%2f) in the path.
Successful 200 OK responses to /api/./users, /api/./roles, or /api/project/../users originating from unauthenticated sessions.
Unusual enumeration patterns targeting /api/* endpoints from a single source IP without preceding login activity.

Detection Strategies

Inspect FUXA and reverse proxy access logs for request paths containing dot-segments and correlate against session or authentication state.
Deploy web application firewall (WAF) rules that flag or block requests with dot-segments in /api/ paths.
Alert on API responses returning user or role JSON structures without a corresponding authenticated session identifier.

Monitoring Recommendations

Forward FUXA HTTP access logs and reverse proxy logs to a centralized SIEM for path-normalization analytics.
Monitor east-west traffic to OT/SCADA hosts for anomalous REST API calls from engineering workstations or unmanaged assets.
Track authentication failure-to-success ratios per source; a source with zero auth events but successful /api/ responses indicates likely bypass.

How to Mitigate CVE-2026-13207

Immediate Actions Required

Restrict network access to FUXA management interfaces using firewalls, VPNs, or ICS network segmentation, and remove any internet exposure.
Place FUXA behind a reverse proxy that performs strict URI normalization and rejects dot-segment paths targeting /api/.
Audit FUXA user and role data for signs of prior unauthorized access, and rotate credentials for accounts that may have been exposed.

Patch Information

Apply the fixed FUXA release when available from the vendor. Monitor the FUXA GitHub release notes for the version that addresses CVE-2026-13207 and remediation guidance published in CISA ICS Advisory ICSA-26-181-02. Verify the deployed version after upgrade and confirm authentication middleware rejects dot-segment paths.

Workarounds

Configure an upstream reverse proxy such as NGINX or Apache to canonicalize paths and return 400 Bad Request for URIs containing /./, /../, or their encoded forms before traffic reaches FUXA.
Enforce network-level allowlisting so only trusted engineering hosts can reach the FUXA HTTP port.
Disable remote access to the FUXA administrative API until a patched version is deployed and validated.

bash

# NGINX reverse proxy example: reject dot-segment paths targeting the FUXA API
location /api/ {
    if ($request_uri ~* "(\.\./|/\./|%2e%2e|%2e/)") {
        return 400;
    }
    proxy_pass http://fuxa_backend;
    proxy_set_header Host $host;
    proxy_set_header X-Real-IP $remote_addr;
}