CVE-2018-3723 in defaults-deep
Summary
by MITRE
defaults-deep node module before 0.2.4 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 • 03/22/2023
The CVE-2018-3723 vulnerability represents a critical prototype pollution issue within the defaults-deep node module version 0.2.3 and earlier. This flaw 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 throughout the application. The vulnerability specifically exploits the unsafe handling of object properties during deep merging operations, allowing malicious input to modify the Object.prototype directly through the _proto_ property.
The technical exploitation occurs when the defaults-deep module processes user-controlled input during object merging operations without proper validation or sanitization of property names. When a malicious user supplies an input object containing properties with names like _proto_ or constructor, the module fails to properly escape or validate these inputs, leading to prototype pollution. This allows attackers to inject malicious properties or methods into the Object.prototype, which then propagates to all objects created in the application context.
The operational impact of this vulnerability is severe as it can lead to various downstream security consequences including remote code execution, denial of service, or data manipulation attacks. When prototype pollution occurs, any object created in the application can inherit the malicious properties, potentially allowing attackers to bypass security controls, manipulate application behavior, or execute unintended code. The vulnerability is particularly dangerous in web applications where user input flows through the defaults-deep module during configuration merging or data processing operations.
Mitigation strategies for CVE-2018-3723 include upgrading the defaults-deep module to version 0.2.4 or later, which implements proper prototype validation and sanitization. Organizations should also implement input validation and sanitization practices for all user-supplied data, particularly when processing configuration files or user inputs that may be merged into application objects. Security monitoring should include detection of unusual object property modifications and prototype pollution attempts. The vulnerability aligns with ATT&CK technique T1059.007 for script injection and T1566 for social engineering, as it often requires initial compromise through user input manipulation to achieve broader system compromise. Additionally, implementing Content Security Policy headers and using secure coding practices that avoid direct prototype manipulation can further reduce the attack surface and prevent exploitation of similar prototype pollution vulnerabilities.