← Vulnerability feed

Vulnerability record · CVE-2026-40933 · published 21 April 2026

CVE-2026-40933: Flowiseai flowise os command injection vulnerability

Flowiseai · Flowise

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.

9.9 CVSS 3.1 Critical EPSS 1.3% · top 31.1% CWE-78 · OS command injection
9.9CVSS 3.1 base score
1.3%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
4References, 2 tagged exploit
17 Jun 2026Last modified by NVD

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.

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/FlowiseAI/Flowise/security/advisories/GHSA-c9gw-hvqq-f33r ExploitVendor Advisory
https://www.ox.security/blog/mcp-supply-chain-advisory-rce-vulnerabilities-across-the-ai-ecosystem Press/Media CoverageThird 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 CoverageThird Party Advisory
https://github.com/FlowiseAI/Flowise/security/advisories/GHSA-c9gw-hvqq-f33r ExploitVendor Advisory

Track CVE-2026-40933 inside VULONE

Watch it alongside the ransomware crews, C2 infrastructure and forum chatter that reference it, query it through the API and pull it into your SIEM over TAXII.

Start free Open in platform

Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

10.0CVE-2025-71338Flowiseai flowise vulnerabilityFlowise through 2.2.7 fails to sanitize path segments in the document-store loader endpoint, allowing unauthenticated attackers to write files outsid…EPSS 1.2%10.0CVE-2025-59528Flowise CustomMCP node code injection enables remote code executionFlowise 3.0.5 passes user-supplied mcpServerConfig input directly into the JavaScript Function() constructor inside convertToValidJSONString, with no…EPSS 86%analysed9.9CVE-2025-61913Flowiseai flowise path traversal vulnerabilityFlowise is a drag & drop user interface to build a customized large language model flow. In versions prior to 3.0.8, WriteFileTool and ReadFileTool i…EPSS 13%9.8CVE-2026-52098Flowiseai flowise code injection vulnerabilityAn issue in Flowise 3.1.2 allows a remote attacker to execute arbitrary code via the /api/v1/prediction/<flowId> endpointEPSS 1.1%9.8CVE-2026-41267Flowiseai flowise insecure direct object reference vulnerabilityFlowise is a drag & drop user interface to build a customized large language model flow. Prior to 3.1.0, an improper mass assignment (JSON injection)…EPSS 0.48%9.8CVE-2026-41268Flowiseai flowise improper input validation vulnerabilityFlowise is a drag & drop user interface to build a customized large language model flow. Prior to 3.1.0, Flowise is vulnerable to a critical unauthen…EPSS 1.2%9.8CVE-2025-58434Flowise forgot-password endpoint leaks reset token, enabling account takeoverFlowise 3.0.5 and earlier returns a valid password reset tempToken and sensitive account details from the forgot-password endpoint without authentica…EPSS 50%analysed9.8CVE-2025-8943Flowise Custom MCPs feature allows unauthenticated OS command executionFlowise's Custom MCPs feature is meant to run OS commands such as npx to start local MCP servers, but the platform's authentication and authorization…EPSS 66%analysed

Source: NIST National Vulnerability Database (record CVE-2026-40933), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.