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CRITICAL severity

GHSA-c9gw-hvqq-f33r — flowise

CRITICAL

GHSA-c9gw-hvqq-f33r is a critical-severity (CVSS 9.9) OS Command Injection vulnerability in flowise. A fix is available for flowise — see the affected versions and patch details below.

Flowise: Authenticated RCE Via MCP Adapters

Also known asCVE-2026-40933
Published
Apr 16, 2026
Updated
Apr 16, 2026
Affected
2 pkgs
Patched
2 / 2
Exploits
None indexed
Exploitation data as of Sep 26, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

Proof-of-concept exploit code exists

  • CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
  • A successful exploit gives an attacker total control of the affected component, not partial access.

Exploitation and automatability from CISA’s SSVC triage for GHSA-c9gw-hvqq-f33r.

EPSS Exploitation Probability

via FIRST.org ↗
1.3%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs69th percentile — riskier than 69% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

GHSA-c9gw-hvqq-f33r by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 379,842 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

2 pkgs affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

0other npm packages depend on this — each one inherits the vulnerability until it's patched upstream
flowisenpm
3Kdownloads / week
flowise-componentsnpm
3Kdownloads / week

Description

Summary

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.

Details

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.

https://github.com/FlowiseAI/Flowise/blob/d848baeb6bd9737a1e7fc912349c45fbdcc7bb38/packages/components/nodes/tools/MCP/core.ts#L223

https://github.com/FlowiseAI/Flowise/blob/d848baeb6bd9737a1e7fc912349c45fbdcc7bb38/packages/components/nodes/tools/MCP/core.ts#L177

https://github.com/FlowiseAI/Flowise/blob/d848baeb6bd9737a1e7fc912349c45fbdcc7bb38/packages/components/nodes/tools/MCP/core.ts#L269

PoC

Create a new Custom MCP and add an "npx -c" command.

{
    "command": "npx",
    "args": [
        "-c",
        "touch /tmp/pwn"
    ]
}
<img width="358" height="628" alt="Screenshot 2026-01-12 at 18 32 37" src="https://github.com/user-attachments/assets/d95c1ae2-23a7-4afe-b586-722003baf50e" />

Impact

This is an authenticated arbitrary command execution due to unsanitized input, even though the input is sanitized, more protections should be added in order to close ways for attackers to execute arbitrary commands.

Affected Packages

2 total 2 fixed
EcosystemPackageVulnerable rangeFix
📦npmflowiseall versions3.1.0npm install flowise@3.1.0
📦npmflowise-componentsall versions3.1.0npm install flowise-components@3.1.0

Affected Products

1 product · 1 configurations
Application
flowiseflowiseai
< 3.1.0
range

Detection & mitigation playbook

Open-source dependency
  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for flowise, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update flowise to 3.1.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-c9gw-hvqq-f33r is resolved across your whole dependency graph.

  3. Workarounds

    Stop passing untrusted input into the interpreter or shell: call the affected binary with an argument array rather than a composed command string, reject anything outside a strict allowlist of expected values, and run the component under an account that cannot reach beyond the work it legitimately does.

Frequently Asked Questions

### Summary 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. ### Details 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
O3 Security · Impact-Aware SCA

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