Prototype Pollution

Vulnerability

Overview

The promisehelpers npm package is vulnerable to Prototype Pollution through its insert function [1][2]. Prototype Pollution is a JavaScript vulnerability that allows an attacker to inject properties into existing object prototypes, such as Object.prototype. This occurs when the insert function recursively merges user-supplied objects without properly sanitizing special keys like __proto__, constructor, or prototype [2].

Exploitation

An attacker can exploit this vulnerability by providing a specially crafted object to the insert function. The malicious object contains a __proto__ property that, when merged, pollutes the global Object.prototype. This attack does not require authentication if the application exposes the insert function to user-controlled input [2]. The attacker can then influence the behavior of all objects in the application by modifying inherited properties.

Impact

Successful exploitation can lead to denial of service by triggering JavaScript exceptions or, more critically, remote code execution. By polluting Object.prototype, an attacker can alter the application's logic, bypass security checks, or inject arbitrary code execution paths [2]. The severity is amplified because the pollution affects all objects in the runtime environment.

Mitigation

All versions of promisehelpers are affected, and no official patch has been released as of the publication date [1]. Users should avoid using this package or implement input validation to prevent the insert function from processing untrusted data. Consider switching to alternative libraries that are not susceptible to prototype pollution.