CVE-2026-69263: Flowise: CVE-2025-8943 Patch Bypass: npm_config_yes bypasses MCP environment variable blocklist (Unauthenticated RCE)

The mitigation shipped for CVE-2025-8943 blocks the -y and --yes flags on npx to stop auto-installation of arbitrary packages. That flag filter works. The environment-variable check in the same patch denies only four variable names by exact string match, and npm reads its configuration directly from npm_config_* environment variables. Setting npm_config_yes=true reproduces the --yes behaviour the flag filter is meant to prevent, so npx auto-installs and executes the named package. The mitigation is fully bypassed.

This works with the MCP security check enabled (CUSTOM_MCP_SECURITY_CHECK=true). On a default Flowise deployment, which ships with no authentication, the result is unauthenticated remote code execution.