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CVE-2026-120338: Prefab UI's Generative UI sandbox runs caller-supplied Python inside Pyodide, Python compiled to WebAssembly, in a Deno subprocess. The feature is documented as
CVE-2026-120338 Nov 1, 2026 Source: Vendor
Prefab UI's Generative UI sandbox runs caller-supplied Python inside Pyodide, Python compiled to WebAssembly, in a Deno subprocess. The feature is documented as isolation for untrusted code, including LLM-written UI. From prefab-ui 0.14.0 through 0.20.2 the launcher starts Deno with unrestricted --allow-read, --allow-write, and --allow-net, and the runner leaves the Deno API on the JavaScript global object. Pyodide's js module proxies that global, so the Python can call Deno.readTextFileSync and
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The credited names below are quoted verbatim from the vendor's own advisory:
https://nvd.nist.gov/vuln/detail/CVE-2026-120338
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