Flowise before 3.1.3 remote code execution in Custom MCP node (stdio)

high severity · published 2026-08-13

Authenticated users can run arbitrary system commands on the Flowise server through the Custom MCP node when CUSTOM_MCP_PROTOCOL is set to stdio. They abuse the PYTHONWARNINGS and BROWSER environment variables with python3, or the root working directory with node, to bypass validation.

Fixed in: 3.1.3

CVE: CVE-2026-73601

Source: NVD

Am I affected?

You are affected if the installed version is older than 3.1.3. Check the version you have and update to 3.1.3 or later. The fixed version is verified against a vendor or advisory source.

Get the fix

FixLane has a reviewed fix procedure for this incident: a read-only check first, then the fix. Ask the Telegram bot, or connect an AI agent to the FixLane MCP server and call get_fix_prompt with incident id 166 and your operating system.