CVE-2018-3720 in assign-deep
Summary
by MITRE
assign-deep node module before 0.4.7 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-2018-3720 vulnerability resides within the assign-deep node module version 0.4.6 and earlier, representing a critical modification of assumed-immutable data flaw that fundamentally compromises object integrity within javascript applications. This vulnerability specifically targets the prototype pollution mechanism by allowing malicious actors to manipulate the Object.prototype through the _proto_ property, creating a widespread impact across all objects in the application's runtime environment. The flaw operates by exploiting the module's failure to properly sanitize input when performing deep assignment operations, enabling attackers to inject malicious prototype modifications that persist throughout the application lifecycle.
The technical execution of this vulnerability leverages javascript's prototype chain mechanism to inject properties into the Object.prototype, which then propagates to all objects inheriting from it. When the assign-deep module processes objects containing _proto_ properties in its assignment logic, it fails to validate or sanitize these inputs, allowing attackers to inject malicious prototype modifications that can alter the behavior of core javascript objects. This represents a classic prototype pollution vulnerability that aligns with CWE-471 and follows patterns documented in the OWASP Top Ten as a critical injection flaw. The attack vector typically involves crafting malicious input data that contains _proto_ or constructor properties, which when processed by the vulnerable module, modifies the global Object.prototype.
The operational impact of CVE-2018-3720 extends far beyond simple data corruption, as it creates persistent security weaknesses that can be exploited across multiple attack surfaces. Applications utilizing vulnerable versions of assign-deep become susceptible to various downstream attacks including but not limited to prototype pollution-based exploitation techniques that can lead to remote code execution in certain contexts. The vulnerability affects the fundamental object model of javascript applications, potentially enabling attackers to modify core object properties, inject malicious methods, or manipulate application behavior in ways that can compromise data integrity and system security. This flaw particularly impacts server-side javascript applications and node.js environments where object manipulation is frequent and deep assignment operations are common.
Mitigation strategies for CVE-2018-3720 primarily focus on immediate version upgrades to assign-deep 0.4.7 or later, which include proper input sanitization and prototype validation mechanisms. Organizations should implement comprehensive dependency scanning and monitoring to identify all instances of vulnerable modules within their application ecosystems, as this vulnerability can propagate through complex dependency trees. Additional defensive measures include implementing prototype pollution detection libraries, adding input validation layers, and configuring application security controls to prevent malicious prototype modifications. The remediation process should also include thorough security testing of application code to ensure that no other modules within the application stack are susceptible to similar prototype pollution vulnerabilities, aligning with ATT&CK technique T1068 which covers exploit for privilege escalation through prototype pollution. Organizations must also consider implementing runtime protections and monitoring systems to detect and prevent prototype pollution attacks in real-time environments.