CVE-2018-3719 in mixin-deep
Summary
by MITRE
mixin-deep node module before 1.3.1 suffers from a Modification of Assumed-Immutable Data (MAID) vulnerability, which allows a malicious user to modify the prototype of "Object" via __proto__, causing the addition or modification of an existing property that will exist on all objects.
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Analysis
by VulDB Data Team • 03/21/2023
The CVE-2018-3719 vulnerability represents a critical prototype pollution flaw in the mixin-deep node module version 1.3.1 and earlier. This vulnerability falls under the CWE-471 category of Modification of Assumed-Immutable Data, where an attacker can manipulate object prototypes in ways that affect all subsequent object instances within the application's runtime environment. The vulnerability specifically arises from the module's improper handling of object property assignment during deep merging operations, allowing malicious input to modify the Object.prototype directly through the _proto_ property mechanism.
The technical exploitation of this vulnerability occurs when the mixin-deep module processes user-controlled input without proper sanitization, enabling attackers to inject malicious prototype modifications. When the module encounters an object with a _proto_ property in its input data, it fails to properly validate or escape this input before merging it into the target object structure. This allows an attacker to inject a payload that modifies the Object.prototype directly, which then propagates to all objects created within the same JavaScript runtime context. The impact extends beyond simple data corruption as it fundamentally alters the behavior of core JavaScript objects and can lead to various downstream security consequences including remote code execution in certain contexts.
The operational impact of CVE-2018-3719 is significant for applications that rely on mixin-deep for object merging operations, particularly in server-side JavaScript environments where user input is processed. Attackers can leverage this vulnerability to manipulate object behavior, potentially leading to privilege escalation, data manipulation, or even arbitrary code execution depending on the application's architecture and how it handles merged objects. The vulnerability is particularly dangerous because it affects the fundamental object model of JavaScript applications, meaning that any object created after the prototype pollution occurs may exhibit unexpected behavior. This makes the vulnerability particularly insidious as it can cause subtle and hard-to-diagnose issues that may not manifest immediately but can lead to severe security implications over time.
Organizations should immediately update to mixin-deep version 1.3.1 or later, which includes proper input validation and sanitization mechanisms to prevent prototype pollution attacks. The fix typically involves implementing strict validation of object properties during merging operations and preventing the propagation of _proto_ and constructor properties from user-controlled input. Security teams should also conduct comprehensive code reviews to identify other potential prototype pollution vulnerabilities in their dependency tree, as this type of vulnerability is common in JavaScript applications and can be found in various utility libraries and object manipulation frameworks. Additionally, implementing runtime protections such as prototype validation checks and Content Security Policy measures can provide additional defense-in-depth against similar attacks, aligning with ATT&CK technique T1059.007 for JavaScript-based attacks and CWE-471 for prototype pollution vulnerabilities.