CVE-2026-40933
Flowise: Authenticated RCE Via MCP Adapters
Description
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.
INFO
Published Date :
April 21, 2026, 10:16 p.m.
Last Modified :
April 23, 2026, 3:40 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | CRITICAL | [email protected] | ||||
| CVSS 3.1 | CRITICAL | MITRE-CVE |
Solution
- Update Flowise to version 3.1.0 or later.
- Review and sanitize MCP adapter configurations.
- Ensure proper input validation for stdio commands.
Public PoC/Exploit Available at Github
CVE-2026-40933 has a 11 public
PoC/Exploit available at Github.
Go to the Public Exploits tab to see the list.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-40933.
| URL | Resource |
|---|---|
| https://github.com/FlowiseAI/Flowise/security/advisories/GHSA-c9gw-hvqq-f33r | Exploit Vendor Advisory |
| https://www.ox.security/blog/mcp-supply-chain-advisory-rce-vulnerabilities-across-the-ai-ecosystem | Press/Media Coverage Third Party Advisory |
| https://www.ox.security/blog/the-mother-of-all-ai-supply-chains-critical-systemic-vulnerability-at-the-core-of-the-mcp | Press/Media Coverage Third Party Advisory |
| https://github.com/FlowiseAI/Flowise/security/advisories/GHSA-c9gw-hvqq-f33r | Exploit Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-40933 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-40933
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
The Project shares all information on MCP related CVE's published
mcp mcp-security mcp-cve
None
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PowerShell Shell
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Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-40933 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-40933 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Apr. 23, 2026
Action Type Old Value New Value Added CPE Configuration OR *cpe:2.3:a:flowiseai:flowise:*:*:*:*:*:*:*:* versions up to (excluding) 3.1.0 Added Reference Type CISA-ADP: https://github.com/FlowiseAI/Flowise/security/advisories/GHSA-c9gw-hvqq-f33r Types: Exploit, Vendor Advisory Added Reference Type GitHub, Inc.: https://github.com/FlowiseAI/Flowise/security/advisories/GHSA-c9gw-hvqq-f33r Types: Exploit, Vendor Advisory Added Reference Type GitHub, Inc.: https://www.ox.security/blog/mcp-supply-chain-advisory-rce-vulnerabilities-across-the-ai-ecosystem Types: Press/Media Coverage, Third Party Advisory Added Reference Type GitHub, Inc.: https://www.ox.security/blog/the-mother-of-all-ai-supply-chains-critical-systemic-vulnerability-at-the-core-of-the-mcp Types: Press/Media Coverage, Third Party Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Apr. 22, 2026
Action Type Old Value New Value Added Reference https://github.com/FlowiseAI/Flowise/security/advisories/GHSA-c9gw-hvqq-f33r -
New CVE Received by [email protected]
Apr. 21, 2026
Action Type Old Value New Value Added Description 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. Added CVSS V3.1 AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H Added CWE CWE-78 Added Reference https://github.com/FlowiseAI/Flowise/security/advisories/GHSA-c9gw-hvqq-f33r Added Reference https://www.ox.security/blog/mcp-supply-chain-advisory-rce-vulnerabilities-across-the-ai-ecosystem Added Reference https://www.ox.security/blog/the-mother-of-all-ai-supply-chains-critical-systemic-vulnerability-at-the-core-of-the-mcp