PYSEC-2026-4241 Langflow: OS command injection (RCE) via arbitrary command in MCP stdio server configuration

Summary Before Langflow 1.10.3, the MCP stdio transport launched whatever command / args a user put in an MCP server configuration, with no allowlist and before 1.10.3 wrapped in bash -c "exec command ...". Any user able to reach the MCP server settings "Settings → MCP Servers → Add MCP Server",...