Remote code execution in Flowise Custom MCP Config Node (CVE-2026-73601)

Flowise deployments with CUSTOM_MCP_PROTOCOL set to stdio (the default setting) are vulnerable to remote code execution through the Custom MCP node, which uses the StdioClientTransport MCP client. Authenticated users can bypass the built-in argument and environment variable validation by abusing environment variables such as PYTHONWARNINGS and BROWSER with python3, or by leveraging the root working directory with node, to execute arbitrary system commands. Affected versions: - npm flowise <= 3.1.2 - npm flowise-components <= 3.1.2 We recommend updating to: 3.1.3. CVSS 9.0 · our assessment: act_now Reference: https://github.com/FlowiseAI/Flowise/security/advisories/GHSA-g98q-rm45-q9h8 Details: https://vuln.today/cve/CVE-2026-73601