CVE-2026-40933

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.

At a glance

Exploitability

Can be exploited over the network with a low-privilege account. High risk of data exposure, data tampering, service disruption.

Exploit odds

12.0% chance of exploitation in the next 30 days (EPSS). Higher than most.

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-04-21 22:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-10-26 22:10 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 12.0% in the next 30 days (EPSS).
• Severity: 9.9 CRITICAL (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2026-04-21 22:16 UTC

Last modified

2026-10-26 22:10 UTC

Exploit probability

12.0% · EPSS, next 30 days

Weakness

CWE-78 · OS command injection

Record status

Analyzed

Affected

• Flowiseai Flowise < 3.1.0

Attack profile CVSS 3.1 · 9.9

Attack vector

Network

Complexity

Low

Privileges needed

Low

User interaction

None

Scope

Changed

Confidentiality

High

Integrity

High

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-40933.md and follow it. Check whether this project is affected by CVE-2026-40933. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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