Staging Environment: Content and features may be unstable or change without notice.
Advisory details: github_osv / GHSA-c9gw-hvqq-f33r
Advisory ID github_osv/GHSA-c9gw-hvqq-f33r
Aliases CVE-2026-40933
Summary Flowise: Authenticated RCE Via MCP Adapters ### 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.
Status Published
Exploitability 0.5
Weighted Severity 8.9
Risk 4.5
Affected and Fixed Packages Package Details
Introduced and Fixed Package Commit Patches Package Commit Patches Details
Weaknesses (1)
CWE-78 Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
System Score Found at
cvssv3.1 9.9 https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/04/GHSA-c9gw-hvqq-f33r/GHSA-c9gw-hvqq-f33r.json
generic_textual CRITICAL
Reference id Reference type URL
https://github.com/FlowiseAI/Flowise
https://github.com/FlowiseAI/Flowise/security/advisories/GHSA-c9gw-hvqq-f33r
https://www.ox.security/blog/mcp-supply-chain-advisory-rce-vulnerabilities-across-the-ai-ecosystem
https://www.ox.security/blog/the-mother-of-all-ai-supply-chains-critical-systemic-vulnerability-at-the-core-of-the-mcp
No exploits are available.

No EPSS data available for this advisory.

Patch URL
There are no known patches.
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H Found at https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/04/GHSA-c9gw-hvqq-f33r/GHSA-c9gw-hvqq-f33r.json
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none

Vector: SSVCv2/E:P/A:N/T:T/P:M/B:A/M:M/D:R/2026-04-22T13:20:05Z/

Decision: Track*

Source URL: https://github.com/cisagov/vulnrichment/blob/develop/2026/40xxx/CVE-2026-40933.json

Source Advisory: vulnrichment/CVE-2026-40933

View SSVC decision tree 
[{'Exploitation': 'poc'},
 {'Automatable': 'no'},
 {'Technical Impact': 'total'},
 {'Mission Prevalence': 'minimal'},
 {'Public Well-being Impact': 'material'},
 {'Mission & Well-being': 'medium'}]