CVE-2026-66747 — Zbtlink router firmware ships an embedded remote-control implant, ENDLESSDOORS, present…¶

Key facts

CVE-2026-66747 is a Critical (9.8) vulnerability: Zbtlink router firmware ships an embedded remote-control implant, ENDLESSDOORS, present…. This entry ships a detection-only PoC and a Docker test lab.


CVE	CVE-2026-66747
Severity	Critical (9.8)
Detection / prevention	—
PoC	poc.py
Source	2026/CVE-2026-66747/

Details¶

English | 한국어

Description¶

Zbtlink router firmware ships an embedded remote-control implant, ENDLESSDOORS, present in every published build across the product line. It is the open-source ycsunjane/rctl tool built in as an OpenWrt package (librctl.so), started at boot and run as root under the process name kworker to blend in with the kernel's [kworker/*] threads. It opens no listening port; it phones home over cleartext TCP to a hardcoded command-and-control server (command channel 7000, interactive-shell callback 7001) with no authentication and no transport encryption, re-attempting contact roughly every 35 seconds. Its command handler passes any received string to popen() as uid=0, and a reserved rctlbash command returns an interactive root shell. Because the channel is unauthenticated and cleartext, control is not limited to whoever planted it: any party that answers at the C2 address, occupies the network path (DNS or route hijack), or acquires the hardcoded fallback domain obtains unauthenticated remote code execution as root.

Vulnerability Details¶

Property	Value
CVE ID	CVE-2026-66747
Type	RCE
CVSS Score	9.8

Proof of Concept¶

Download¶

# Download PoC script
curl -O https://raw.githubusercontent.com/fankh/vulnerability-poc/main/2026/CVE-2026-66747/poc.py

Usage¶

# Run PoC against target
python3 poc.py --target <TARGET_URL>

# With authentication
python3 poc.py --target <TARGET_URL> --username <USER> --password <PASS>

⚠️ Warning: This PoC is for authorized security testing only. It uses detection-only techniques and does not exploit or damage target systems.

Test Lab¶

This repository includes a Docker-based test environment with both vulnerable and patched applications.

Quick Start¶

# Clone and navigate to CVE directory
cd CVE-2026-66747

# Start both applications
docker-compose up -d

# Run tests
./run-tests.sh    # Linux/Mac
./run-tests.ps1   # Windows PowerShell

Application Endpoints¶

Application	URL	Status
Vulnerable App	http://localhost:8080	Shows vulnerability
Patched App	http://localhost:8081	Demonstrates fix

Directory Structure¶

├── README.md           # English documentation
├── README_KO.md        # Korean documentation
├── poc.py              # PoC detection script
├── docker-compose.yml  # Container orchestration
├── run-tests.sh        # Linux/Mac test runner
├── run-tests.ps1       # Windows test runner
├── vulnerable-app/     # Vulnerable version
│   ├── app.py
│   ├── Dockerfile
│   └── requirements.txt
└── patched-app/        # Fixed version
    ├── app.py
    ├── Dockerfile
    └── requirements.txt

References¶

https://github.com/ycsunjane/rctl
https://www.vulncheck.com/advisories/zbt-endlessdoors
https://www.vulncheck.com/blog/zbt-endlessdoors
https://www.zbtlink.com/pages/zbt-router-firmware-download

Generated by PoC Generator on 2026-08-10T02:21:56.31526533

Frequently asked questions¶

What is CVE-2026-66747?¶

CVE-2026-66747 is a Critical (9.8) vulnerability: Zbtlink router firmware ships an embedded remote-control implant, ENDLESSDOORS, present…. This entry ships a detection-only PoC and a Docker test lab.

How do I detect CVE-2026-66747?¶

Run the detection-only PoC included with this entry against your Docker test lab to confirm whether a target is affected; pair it with your own IDS logging.

How do I block or mitigate CVE-2026-66747?¶

Upgrade to a fixed version per the vendor advisory; the NVD record lists the affected versions. Use the included PoC to verify your remediation.

For authorized security testing and research only. See the full source and NVD record.