CVE-2018-3750 in deep-extend
Summary
by MITRE
The utilities function in all versions <= 0.5.0 of the deep-extend 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 • 04/03/2023
The deep-extend node module vulnerability CVE-2018-3750 represents a critical prototype pollution flaw that affects all versions up to and including 0.5.0. This vulnerability resides within the utility function of the deep-extend package, which is commonly used for deep merging JavaScript objects. The flaw occurs when attacker-controlled data is passed through this function, enabling manipulation of the Object prototype itself. This type of vulnerability falls under CWE-471, which specifically addresses the modification of objects during serialization or deserialization processes. The vulnerability is particularly dangerous because it allows attackers to inject malicious properties into the Object prototype, which then propagates to all objects in the JavaScript runtime environment.
The technical exploitation of this vulnerability occurs through careful construction of input data that gets processed by the vulnerable deep-extend function. When the function processes attacker-controlled data, it recursively merges objects without proper validation of property names, allowing malicious keys such as _proto_ or constructor to be injected into the prototype chain. This prototype pollution can be leveraged to modify the behavior of all objects in the application, potentially leading to arbitrary code execution, denial of service, or data manipulation. The vulnerability is classified as a prototype pollution attack under the MITRE ATT&CK framework, specifically mapping to technique T1059.007 for script injection and T1566 for social engineering. The impact is amplified because many JavaScript applications rely on object prototypes for their core functionality, making this vulnerability particularly dangerous in web applications and server-side environments.
The operational consequences of CVE-2018-3750 extend far beyond simple property modification, as it can lead to complete system compromise when combined with other vulnerabilities or attack vectors. Applications using vulnerable versions of deep-extend are at risk of having their prototype chain manipulated, which can result in unexpected behavior, security bypasses, or even remote code execution in certain contexts. The vulnerability is particularly concerning in Node.js environments where prototype pollution can be exploited to manipulate core JavaScript objects, affecting everything from user sessions to application logic. This flaw demonstrates the critical importance of input validation and proper object handling in JavaScript applications, as it can be exploited by attackers who gain control over any part of the object structure being merged. Organizations using vulnerable versions of this module should immediately update to patched versions or implement alternative deep merge implementations that properly sanitize input data to prevent prototype pollution attacks. The vulnerability highlights the need for comprehensive security testing of third-party dependencies and demonstrates how seemingly minor flaws in utility functions can have catastrophic security implications across entire applications.