CVE-2018-16491 in node.extend
Summary
by MITRE
A prototype pollution vulnerability was found in node.extend <1.1.7, ~<2.0.1 that allows an attacker to inject arbitrary properties onto Object.prototype.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 05/07/2020
The vulnerability identified as CVE-2018-16491 represents a critical prototype pollution flaw within the node.extend library version 1.1.6 and earlier versions of the 2.x branch. This issue stems from improper handling of object property assignment during deep cloning operations, allowing attackers to manipulate the Object.prototype chain through crafted input data. The vulnerability manifests when applications use the extend library to merge configuration objects or process user-supplied data, creating a persistent security risk that can affect multiple downstream components.
The technical root cause of this vulnerability lies in the library's failure to properly sanitize property names during object merging operations. When the extend function processes objects containing specially crafted property names such as _proto_ or constructor, it directly assigns these properties to the target object without adequate validation. This behavior enables attackers to inject malicious properties into the Object.prototype, which then propagates to all objects in the JavaScript runtime environment. The flaw operates at the core of JavaScript's prototype inheritance mechanism, making it particularly dangerous as it affects the fundamental object model rather than just specific application code.
The operational impact of CVE-2018-16491 extends far beyond the immediate library usage context, creating cascading security implications across affected applications. Once an attacker successfully pollutes the prototype, they can potentially manipulate object behavior, bypass security controls, or even execute arbitrary code in certain runtime environments. This vulnerability aligns with CWE-471, which describes the injection of data into a prototype, and represents a classic example of how seemingly benign library functions can create critical security risks. The attack vector typically involves providing malicious input that gets processed through the vulnerable extend function, making it particularly insidious as it can be exploited through various user interaction points including API endpoints, configuration files, or user input fields.
Mitigation strategies for this vulnerability require immediate library version updates to 1.1.7 or greater for the 1.x branch, or to version 2.0.1 or higher for the 2.x branch where the prototype pollution protection has been implemented. Organizations should conduct comprehensive vulnerability assessments to identify all applications and services utilizing the affected library versions, implementing both automated patching processes and manual code reviews to ensure complete remediation. Additionally, developers should adopt defensive programming practices such as validating object property names before processing, implementing input sanitization routines, and using modern JavaScript features like Object.freeze() or Proxy objects to prevent prototype manipulation. The vulnerability demonstrates the importance of supply chain security and highlights how third-party dependencies can introduce critical risks that require continuous monitoring and updating to maintain application security posture.