CVE-2026-40933Public exploitNetwork attack vector

Authenticated command execution via unsafe MCP arguments

Published Apr 21, 2026 · Updated Apr 21, 2026

OS command injection in FlowiseAI Flowise's Custom MCP adapter before 3.1.0 allows remote authenticated users to execute arbitrary commands. The adapter accepts npx as an allowed executable but fails to reject attacker-controlled -c arguments before launching the stdio transport. Any authenticated user who can add a Custom MCP stdio server can run commands with the Flowise service account's OS privileges.

CVSS severity9.9
Critical
EPSS probability11.96%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

OS command injection in FlowiseAI Flowise's Custom MCP adapter before 3.1.0 allows remote authenticated users to execute arbitrary commands. The adapter accepts npx as an allowed executable but fails to reject attacker-controlled -c arguments before launching the stdio transport. Any authenticated user who can add a Custom MCP stdio server can run commands with the Flowise service account's OS privileges.

The record

CVE
CVE-2026-40933
Published
Apr 21, 2026
Updated
Apr 21, 2026
Vendor
FlowiseAI
Product
Flowise
Classifications
CWE-78, T1059
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 21, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 21, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 3.1.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

FlowiseAI · Flowiseversion=< 3.1.0
FlowiseAI · flowise-componentsversion=< 3.1.0

Published CVSS scores

9.9GitHubCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-78Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
T1059Command and Scripting Interpreter

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo