Skip to content
Fencer Vulns
critical 10.0

CVE-2026-40933 in the critical feed json

Flowise: Authenticated RCE Via MCP Adapters

published 2026-04-16 6 mo ago modified 2026-10-26 13 d ago also GHSA-c9gw-hvqq-f33r , EUVD-2026-24489

cvss
10.0
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
12.0%
EPSS 12.0% chance of exploitation in 30 days, percentile 96%
public exploits
0
none known

Summary

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.

Patch / fix

  • npm flowise 3.1.0
  • npm flowise-components 3.1.0
  • flowiseai flowise 3.1.0

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
total
Assessed
6 mo ago

Exploit prediction

11.96% chance of exploitation in the next 30 days, higher than 96% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/FlowiseAI/Flowise/security/advisories/GHSA-c9gw-hvqq-f33r referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 10.0 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
GitHub 3.1 9.9 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

Affected packages

ecosystem package affected fixed in
npm flowise
<3.1.0
3.1.0
npm flowise-components
<3.1.0
3.1.0

Affected products

  • FlowiseAI Flowise
  • FlowiseAI flowise-components

Classification

Weakness
  • CWE-78 Improper Neutralization of Special Elements used in an OS Command

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.