CVE-2018-3752 in merge-options
Summary
by MITRE
The utilities function in all versions <= 1.0.0 of the merge-options node module can be tricked into modifying the prototype of Object when the attacker can control part of the structure passed to this function. This can let an attacker add or modify existing properties that will exist on all objects.
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Analysis
by VulDB Data Team • 02/24/2020
The CVE-2018-3752 vulnerability resides in the merge-options node module, specifically affecting all versions up to and including 1.0.0. This represents a critical prototype pollution vulnerability that exploits the utilities function to manipulate Object prototypes through attacker-controlled input structures. The vulnerability stems from improper handling of object merging operations where the module fails to properly validate or sanitize input parameters before incorporating them into the prototype chain. When an attacker can influence the structure passed to the merge-options function, they gain the ability to inject malicious properties that will persist across all objects in the JavaScript runtime environment.
The technical flaw manifests in the module's failure to implement proper prototype isolation during object merging operations. When processing user-controllable data structures, the vulnerable function does not adequately check for prototype-polluting keys such as constructor, _proto_, or other properties that could alter the fundamental object prototype chain. This allows attackers to inject properties that become part of the Object.prototype, thereby affecting every object instance in the application's memory space. The vulnerability operates under CWE-471, which classifies it as a modification of the object prototype, and aligns with ATT&CK technique T1059.001 for executing malicious code through prototype pollution.
The operational impact of this vulnerability is severe and far-reaching, as it enables attackers to manipulate core JavaScript object behaviors across the entire application. Once an attacker successfully pollutes the prototype, they can potentially modify or add properties that will be accessible to all subsequent object instances, including those created by the application's own code. This could lead to arbitrary code execution, data manipulation, or privilege escalation within the application context. The vulnerability is particularly dangerous because it can be exploited through various attack vectors including API endpoints, user input processing, or configuration file parsing where the merge-options function might be invoked with untrusted data. The prototype pollution can be leveraged to bypass security controls, manipulate application logic, or create persistent backdoors that remain active throughout the application's lifecycle.
Mitigation strategies for CVE-2018-3752 require immediate remediation through version upgrading to 1.0.1 or later, which addresses the prototype pollution vulnerability through proper input validation and prototype isolation. Organizations should implement comprehensive input sanitization measures to prevent untrusted data from reaching the merge-options function, particularly in scenarios involving user-controllable parameters. Additionally, security teams should deploy runtime monitoring solutions to detect prototype pollution attempts and implement proper object validation patterns that prevent modification of core prototype properties. The fix typically involves ensuring that the merge function properly handles prototype-polluting keys by either rejecting them or safely incorporating them into the target object rather than the prototype chain. Regular security auditing of node modules and dependency management practices should include vulnerability scanning to prevent similar issues from being introduced through third-party libraries in the application stack.