CVE-2023-3696: Critical Prototype Pollution Vulnerability in Mongoose

A piercing siren echoes in the realm of cybersecurity as a severe security flaw, branded as CVE-2023-3696, infiltrates the open-source software Mongoose, the MongoDB object modeling tool famed for its versatility in asynchronous environments. The bug, which carries a significant Common Vulnerability Scoring System (CVSS) score of 10, stands testimony to its gravity and potential for wreaking havoc.

Mongoose, renowned for providing a comprehensive, schema-based solution for application data modeling, caters to the Node.js and Deno platforms. With an all-inclusive package offering features like type casting, validation, query building, and business logic hooks, Mongoose underpins countless modern applications.

However, this prototype pollution vulnerability stands as an ominous threat to its credibility and the security of those applications. This flaw unveils an intricate scenario where an attacker, given a gateway to manipulate an object on the Mongo server, can trigger prototype pollution on any Mongoose client.

Imagine a situation where an inadequately implemented service permits a user to govern the object in functions like findByIdAndUpdate. The trespasser can exploit the $rename operator to activate this bug. Alternatively, consider a scenario involving two distinct services interacting with the same Mongo database, one of which allows the injection of an arbitrary object encapsulating a __proto__ field, thereby triggering this alarming vulnerability.

The perilous implications of this flaw are accentuated when used in tandem with Express and EJS, where it can smoothly translate into Remote Code Execution (RCE). Upon encountering malicious documents and reading them into an object, Mongoose employs an object with a prototype. If the top-level object encompasses a __proto__ field, it instigates an overwrite of the object prototype, a subtle yet sinister mechanism with dramatic repercussions.

This flaw doesn’t stop at compromising data security. It carries the potential for a debilitating Denial-of-Service (DoS) attack, contingent on the size of the Mongo collection and the corresponding libraries implemented in the application. Alarmingly, numerous other libraries are also susceptible to known prototype pollution exploits, exacerbating the overall impact.

The discovery of this critical flaw is attributed to the meticulous efforts of cybersecurity researchers @ehhthing and @strellic_. The revelation has led to the publication of intricate technical details and an illuminating proof-of-concept.

The CVE-2023-3696 vulnerability, known to affect Mongoose version 7.3.2, has fortunately been addressed in version 7.3.3.