CVE-2025-66457: Elysia affected by arbitrary code injection through cookie config

Arbitrary code execution from cookie config. If dynamic cookies are enabled (ie there exists a schema for cookies), the cookie config is injected into the compiled route without first being sanitised.

Availability of this exploit is generally low, as it requires write access to either the Elysia app's source code (in which case the vulnerability is meaningless) or write access to the cookie config (perhaps where it is assumed to be provisioned by the environment).

However when combined with GHSA-hxj9-33pp-j2cc, this vulnerability allows for a full RCE chain.

Impact - aot enabled (default) - cookie schema passed to route - Cookie config controllable eg. via env

Example of vulnerable code js new Elysia({ cookie: { secrets: ' + console.log('pwned from secrets') + ' }, }) .get("/", () => "hello world", { cookie: t.Cookie({ foo: t.Any(), }), })

POC: https://github.com/sportshead/elysia-poc

Patches Patched by 1.4.17 (https://github.com/elysiajs/elysia/pull/1564)

Reference commit: - https://github.com/elysiajs/elysia/pull/1564/commits/26935bf76ebc43b4a43d48b173fc853de43bb51e - https://github.com/elysiajs/elysia/pull/1564/commits/3af978663e437dccc6c1a2a3aff4b74e1574849e

Workarounds Sanitize cookie-related env input

typescript const overrideUnsafeQuote = (value: string) => // '' + value + '' '' + value.replace(/'/g, '\\').replace(/\${/g, '$\\{') + ''