Flowise Sandbox Escape to RCE

============================================================================= Security Advisory elttam Topic: Flowise JavaScript Sandbox Escape Module: FlowiseAI/Flowise, FlowiseAI/nodevm Disclosed: 11-Apr-2026 Credits: Luke Jahnke and Alex Brown Affects: `FlowiseAI/Flowise 3.1.1`, `FlowiseAI/nodevm 3.9.25` # I. Background Flowise AI is an open-source, low-code platform for building AI applications, such as chatbots, workflows, and autonomous agents, through an intuitive drag-and-drop interface, minimising the need for extensive coding. The platform also enables execution of custom JavaScript within a sandboxed environment via the Custom Function Agent Flow node or Custom Tool. By default, this sandbox is powered by `patriksimek/vm2`, a fork of the `patriksimek/vm2` package. # II. Problem Description **NOTE**: This vulnerability still impacts commit `dddfb3c90eec900d747790a439bd362a764039cd` (the latest commit on the main branch at the time of writing). The original report was incorrectly closed, due to a misunderstanding that the report was about the use of an outdated and vulnerable version of the `patriksimek/vm2` sandbox. The sandbox escape that this report documents is an issue with Flowise, and patching the `vm2` sandbox would not resolve it. The `patriksimek/vm2` sandbox executes JavaScript within the same Node.js process, which introduces significant security limitations and makes safely isolating untrusted code inherently difficult. Due to these concerns, the maintainers had deprecated the project and previously issued the following warning: *https://github.com/n8n-io/vm2* > The library contains critical security issues and should not be used in production. Maintenance has been discontinued. Consider migrating to `isolated-vm`. To demonstrate the risks associated with the use of the `vm2` sandbox, a sandbox escape specific to Flowise was investigated. The code snippet below shows the allowed modules that could be used within custom JavaScript code on Flowise. https://github.com/FlowiseAI/Flowise/blob/flowise%403.1.1/packages/components/src/utils.ts#L124 ```ts const defaultAllowExternalDependencies = ['axios', 'moment', 'node-fetch'] <1> ``` <1> Allows custom JavaScript code to use the `axios`, `moment` and `node-fetch` dependencies. Notably, the `moment` dependency had a previously reported path traversal vulnerability (`CVE-2022-24785`) that could lead to RCE when user input is passed to the `locale` function. The patch for `CVE-2022-24785` was implementing regex check to disallow `/` or `\` characters within a locale name, as shown in the code snippet below. *Patch for `CVE-2022-24785` in `moment` (https://github.com/moment/moment/commit/4211bfc8f15746be4019bba557e29a7ba83d54c5)* ```js function isLocaleNameSane(name) { // Prevent names that look like filesystem paths, i.e contain '/' or '\' return name.match('^[^/\\\\]*#x27;) != null; <1> } function loadLocale(name) { var oldLocale = null, aliasedRequire; // TODO: Find a better way to register and load all the locales in Node if ( locales[name] === undefined && typeof module !== 'undefined' && module && module.exports && isLocaleNameSane(name) <1> ) { try { oldLocale = globalLocale._abbr; aliasedRequire = require; aliasedRequire('./locale/' + name); <2> getSetGlobalLocale(oldLocale); } catch (e) { // mark as not found to avoid repeating expensive file require call causing high CPU // when trying to find en-US, en_US, en-us for every format call locales[name] = null; // null means not found } } return locales[name]; } ``` <1> Performs a regex check to disallow `/` or `\` characters within the provided lo

CVSS 4.0

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

Severity from

GitHub (reviewed advisory)

Weakness

CWE-95

Also known as

CVE-2026-69253

• github.com/FlowiseAI/Flowise/security/advisories/GHSA-wg86-r78f-74mp
• github.com/FlowiseAI/Flowise/pull/6417
• github.com/FlowiseAI/Flowise/commit/3f257bdc8196082a178da7134a075824401b13b9
• github.com/FlowiseAI/Flowise
• github.com/FlowiseAI/Flowise/releases/tag/flowise@3.1.3