{"resultsPerPage":1,"startIndex":0,"totalResults":1,"format":"NVD_CVE","version":"2.0","timestamp":"2026-11-02T23:15:24.880","vulnerabilities":[{"cve":{"id":"CVE-2026-120338","sourceIdentifier":"reefs@jfrog.com","published":"2026-11-01T16:18:14.970","lastModified":"2026-11-02T20:17:40.677","vulnStatus":"Deferred","cveTags":[],"descriptions":[{"lang":"en","value":"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 Deno.writeTextFileSync. A caller who can supply the code can read and write files as the server OS user, and can persist code execution by writing a .pth file into the server virtualenv's site-packages. The usual remote path is FastMCP's GenerativeUI provider, which registers the MCP tool generate_prefab_ui and forwards that tool's code argument into this sandbox. On a FastMCP server with no authentication configured, any client who can reach the server can call the tool. With authentication, any client allowed to call tools can. Generative UI is opt-in, and the host must have Deno installed. Confirmed on prefab-ui 0.20.2. Fixed in 0.21.0: after the runtime and Prefab sources load, the runner revokes Deno read, write, and network permission before it accepts code, the process is started with --no-prompt so a permission request cannot grant them again, and bootstrap network access is limited to cdn.jsdelivr.net. The fix is commit 030f074 (pull request 538)."}],"affected":[{"source":"reefs@jfrog.com","affectedData":[{"vendor":"PrefectHQ","product":"prefab-ui","defaultStatus":"unaffected","collectionURL":"https://pypi.org/project/prefab-ui/","packageName":"prefab-ui","programFiles":["src/prefab_ui/sandbox/_pyodide.py","src/prefab_ui/sandbox/runner.js"],"repo":"git://github.com/PrefectHQ/prefab","versions":[{"version":"0.14.0","lessThan":"0.21.0","versionType":"semver","status":"affected"}]}]}],"metrics":{"cvssMetricV31":[{"source":"reefs@jfrog.com","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","baseScore":10.0,"baseSeverity":"CRITICAL","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"CHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"},"exploitabilityScore":3.9,"impactScore":6.0}],"ssvcV203":[{"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","ssvcData":{"timestamp":"2026-11-02T19:42:39.981153Z","id":"CVE-2026-120338","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}]},"weaknesses":[{"source":"reefs@jfrog.com","type":"Secondary","description":[{"lang":"en","value":"CWE-94"},{"lang":"en","value":"CWE-269"},{"lang":"en","value":"CWE-693"}]}],"references":[{"url":"https://github.com/PrefectHQ/prefab","source":"reefs@jfrog.com"},{"url":"https://github.com/PrefectHQ/prefab/commit/030f074f85e0b1be0dd44b0283185aecb26337a2","source":"reefs@jfrog.com"},{"url":"https://github.com/PrefectHQ/prefab/pull/538","source":"reefs@jfrog.com"},{"url":"https://github.com/PrefectHQ/prefab/releases/tag/v0.14.0","source":"reefs@jfrog.com"},{"url":"https://github.com/PrefectHQ/prefab/releases/tag/v0.20.2","source":"reefs@jfrog.com"},{"url":"https://github.com/PrefectHQ/prefab/releases/tag/v0.21.0","source":"reefs@jfrog.com"},{"url":"https://github.com/PrefectHQ/prefab/security/advisories/GHSA-595q-jv4r-q7j9","source":"reefs@jfrog.com"},{"url":"https://pypi.org/project/prefab-ui/","source":"reefs@jfrog.com"},{"url":"https://pypi.org/project/prefab-ui/0.21.0/","source":"reefs@jfrog.com"}]}}]}