---
title: "CVE-2026-40933: Flowise: Authenticated RCE Via MCP Adapters"
url: https://erroneo.us/security/cve/CVE-2026-40933/
description: "CVE-2026-40933 (flowise (npm)): Flowise is a drag & drop user interface to build a customized large language model flow. Prior to 3.1.0, due to unsafe…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-04-21
date_modified: 2026-04-22
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-40933"
kev: false
cvss: 10
epss: 0.01283
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-40933: Flowise: Authenticated RCE Via MCP Adapters

**Signal:** Critical, preconditions apply. Severe if exploited, but exploitation needs conditions that may not apply to you. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Not in CISA KEV , but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
- EPSS 1.3% , percentile 70: FIRST’s model estimates a 1.3% chance of exploitation activity in the next 30 days, higher than 70% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
- Needs an account (low (any account)). Exposure depends on who can log in.
- Only applies if your dependency tree includes flowise (npm) <= 3.0.13, fixed in 3.1.0 ; flowise-components (npm) <= 3.0.13, fixed in 3.1.0 . Check your lockfile, including transitive dependencies.

## What it is

Flowise is a drag & drop user interface to build a customized large language model flow. Prior to 3.1.0, due to unsafe serialization of stdio commands in the MCP adapter, an authenticated attacker can add an MCP stdio server with an arbitrary command, achieving command execution. The vulnerability lies in a bug in the input sanitization from the “Custom MCP” configuration in http://localhost:3000/canvas - where any user can add a new MCP, when doing so - adding a new MCP using stdio, the user can add any command, even though your code have input sanitization checks such as validateCommandInjection and validateArgsForLocalFileAccess, and a list of predefined specific safe commands - these commands, for example "npx" can be combined with code execution arguments ("-c touch /tmp/pwn") that enable direct code execution on the underlying OS. This vulnerability is fixed in 3.1.0.

## Affected packages

- npm `flowise` <= 3.0.13 → fixed: 3.1.0
- npm `flowise-components` <= 3.0.13 → fixed: 3.1.0

## Affected products (CVE record)

- FlowiseAI Flowise: < 3.1.0
- FlowiseAI flowise-components: < 3.1.0

## Severity

- GitHub_M CVSS 3.1: 10 `CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H`
- GitHub CVSS 3.1: 9.9 `CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation poc , automatable no , technical impact total .
- FIRST EPSS (model of 2026-10-21): 1.28% probability of exploitation activity in the next 30 days; percentile 70.

## Sources

- [GitHub Advisory GHSA-c9gw-hvqq-f33r](https://github.com/advisories/GHSA-c9gw-hvqq-f33r)
- [CVE.org record CVE-2026-40933](https://www.cve.org/CVERecord?id=CVE-2026-40933)
- [NVD entry CVE-2026-40933](https://nvd.nist.gov/vuln/detail/CVE-2026-40933)
- [github.com](https://github.com/FlowiseAI/Flowise/security/advisories/GHSA-c9gw-hvqq-f33r)
- [ox.security](https://www.ox.security/blog/mcp-supply-chain-advisory-rce-vulnerabilities-across-the-ai-ecosystem)
- [ox.security](https://www.ox.security/blog/the-mother-of-all-ai-supply-chains-critical-systemic-vulnerability-at-the-core-of-the-mcp)

---
Source page: https://erroneo.us/security/cve/CVE-2026-40933/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt