CVE-2026-71243 — The backmeup npm package assembles shell command strings by directly concatenating its…¶

Key facts

CVE-2026-71243 is a High (8.8) vulnerability: The backmeup npm package assembles shell command strings by directly concatenating its…. This entry ships a detection-only PoC and a Docker test lab.


CVE	CVE-2026-71243
Severity	High (8.8)
Detection / prevention	—
PoC	poc.py
Source	2026/CVE-2026-71243/

Details¶

English | 한국어

Description¶

The backmeup npm package assembles shell command strings by directly concatenating its option values (name, source, destination, filter) - e.g. cmd = "mkdir -p " + path.join(info.destination, info.name) + "; " - and executes the resulting string through a shell via ssh2-exec (locally via child_process, or remotely via SSH when an ssh handle is supplied), rather than using execFile/spawn with an argument array. The only processing applied is path.normalize()/path.join(), which do not neutralize shell metacharacters (;, |, &, $(), backticks, newline). Any application that passes attacker-influenced values into these options (e.g. a user-chosen backup name) is vulnerable to arbitrary OS command execution on the backup host, or on the remote SSH target when one is configured.

Vulnerability Details¶

Property	Value
CVE ID	CVE-2026-71243
Type	RCE
CVSS Score	8.8

Proof of Concept¶

Download¶

# Download PoC script
curl -O https://raw.githubusercontent.com/fankh/vulnerability-poc/main/2026/CVE-2026-71243/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-2026-71243

# 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/adaltas/node-backmeup

Generated by PoC Generator on 2026-08-10T00:11:26.902424135

Frequently asked questions¶

What is CVE-2026-71243?¶

CVE-2026-71243 is a High (8.8) vulnerability: The backmeup npm package assembles shell command strings by directly concatenating its…. This entry ships a detection-only PoC and a Docker test lab.

How do I detect CVE-2026-71243?¶

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-2026-71243?¶

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.