CVE-2018-16486 in defaults-deep
Summary
by MITRE
A prototype pollution vulnerability was found in defaults-deep <=0.2.4 that would allow a malicious user to inject properties onto Object.prototype.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 05/07/2020
This vulnerability represents a critical prototype pollution flaw in the defaults-deep npm package version 0.2.4 and earlier, where malicious users can inject arbitrary properties onto the Object.prototype object through crafted input data. The vulnerability stems from the package's improper handling of nested object properties during deep merging operations, allowing attackers to manipulate the prototype chain of all objects in the application. When the defaults-deep library processes user-supplied data, it fails to properly validate or sanitize nested property names, enabling attackers to inject properties that persist across all object instances in the JavaScript environment. This flaw specifically affects applications that rely on the defaults-deep library for configuration merging or object initialization, creating a persistent security risk that can be exploited across the entire application lifecycle. The vulnerability is classified as a prototype pollution issue under CWE-471, which occurs when a program modifies the prototype of built-in objects, leading to potential code execution or denial of service scenarios. According to ATT&CK framework, this vulnerability maps to T1211 - Exploitation for Privilege Escalation and T1059 - Command and Scripting Interpreter, as it enables attackers to manipulate object behavior and potentially execute malicious code through prototype manipulation.
The operational impact of CVE-2018-16486 extends beyond simple data corruption, as prototype pollution can lead to severe application compromise scenarios. When attackers pollute the Object.prototype, they can cause existing application code to behave unexpectedly, potentially leading to privilege escalation, denial of service, or even remote code execution in certain contexts. The vulnerability is particularly dangerous because it affects the fundamental object model of JavaScript applications, making it difficult to detect and mitigate. Applications using vulnerable versions of defaults-deep may experience unexpected behavior when processing user input, as the polluted prototype properties can interfere with normal object operations. The flaw is especially concerning in server-side JavaScript environments where applications may perform deep merging operations on user-provided configuration data, creating an attack surface that can be exploited through various input vectors including API endpoints, file uploads, or configuration management interfaces. The vulnerability can be exploited in scenarios where applications deserialize user-controlled data without proper validation, allowing attackers to inject malicious properties that persist across all object instances in the application's memory space.
Mitigation strategies for CVE-2018-16486 require immediate action to update the defaults-deep package to version 0.2.5 or later, which contains the necessary patches to prevent prototype pollution. Organizations should conduct comprehensive vulnerability assessments to identify all applications and dependencies using vulnerable versions of the library, implementing automated dependency scanning tools to prevent similar issues in the future. The recommended approach includes implementing input validation and sanitization measures at all application boundaries, particularly where user data is processed or merged with default configurations. Security teams should also consider implementing prototype pollution detection mechanisms and monitoring for unusual object property modifications in application logs. Additionally, developers should adopt secure coding practices that avoid direct assignment to prototype properties and implement proper object property validation during data processing. The mitigation strategy should align with industry best practices for JavaScript security, including the use of linters and static analysis tools that can detect potential prototype pollution vulnerabilities in code repositories. Organizations must also establish dependency management policies that enforce regular security updates and vulnerability monitoring to prevent exploitation of similar issues in other third-party libraries.