Chawdamrunal

Name of the Vulnerable Software and Affected Versions SandboxJS versions prior to 0.8.36 Description A scope modification vulnerability exists in SandboxJS, specifically in versions 0.8.35 and below. Untrusted sandboxed code can leak internal interpreter objects through the `new` operator, exposing sandbox scope objects to untrusted code. While code evaluation and prototypes remain protected, this allows modification of scopes within the sandbox. The root cause is missing sanitization steps in the `New` operator handler within the `src/executor.ts` file (lines 1275–1280). Specifically, constructor arguments are not sanitized using `valueOrProp()`, and the return value is not sanitized using `getGlobalProp()` or `sanitizeArray()`. This contrasts with the `Call` handler, which correctly sanitizes both arguments and return values. The vulnerability allows an attacker to access real host JavaScript objects, such as `globalThis`, `Function`, and `eval`, through a `Prop` object, and then store a reference to the sandbox's scope within a constructed object. A proof of concept demonstrates the ability to leak the scope object by creating a constructor that captures the `isNaN` object's context. The attack requires no authentication or user interaction and works with the default sandbox configuration. Recommendations Update to SandboxJS version 0.8.36 or later to address the vulnerability. As a critical fix, sanitize constructor arguments in the `New` operator handler by adding `valueOrProp()` to the arguments array. Implement deep sanitization of sandbox return values to strip internal references. Freeze or seal the `options.globals` and `scope.allVars` objects after construction to prevent mutation.