Prefab UI sandbox lets Python code read and write server files

critical severity · published 2026-11-01

The Generative UI sandbox starts Deno with unrestricted file read, write and network permissions and leaves the Deno API reachable from the Python it runs. Anyone who can supply the sandbox code, including LLM-written UI, can read and write files as the server's OS user.

Fixed in: 0.21.0

CVE: CVE-2026-120338

Source: NVD

Am I affected?

You are affected if the installed version is older than 0.21.0. Check the version you have and update to 0.21.0 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 666 and your operating system.