CVE-2020-8203: High Vulnerability In Lodash.set-4.3.2

by Alex Johnson 54 views

This article discusses the high-severity vulnerability CVE-2020-8203 detected in lodash.set-4.3.2, a widely used JavaScript utility library. We will delve into the details of the vulnerability, its potential impact, and the recommended steps to mitigate the risk. This comprehensive analysis aims to provide developers and security professionals with a clear understanding of the issue and how to address it effectively.

Understanding CVE-2020-8203

CVE-2020-8203 identifies a prototype pollution vulnerability affecting versions of lodash prior to 4.17.20. Prototype pollution is a type of security vulnerability that allows an attacker to manipulate the properties of JavaScript object prototypes. This can lead to unexpected behavior, denial of service, or even remote code execution in certain circumstances. In the case of lodash.set, the vulnerability stems from the way the _.set and _.zipObjectDeep methods handle object property assignment. These methods, when used with carefully crafted input, can be exploited to modify the global object prototype, potentially affecting all objects in the application.

The Vulnerable Library: lodash.set-4.3.2

The specific library in question is lodash.set-4.3.2, a module that exports the _.set method from the popular lodash library. Lodash is a comprehensive toolkit of JavaScript utilities that provides a wide range of functions for common programming tasks, such as array manipulation, object handling, and function binding. The _.set method is used to set the value of a property at a specified path in an object. While lodash is generally considered a reliable and well-maintained library, this vulnerability highlights the importance of staying up-to-date with security patches and best practices.

The library can be found at the following URL: https://registry.npmjs.org/lodash.set/-/lodash.set-4.3.2.tgz

Dependency Path

The vulnerability was discovered in the context of the mongo-express project, specifically within the following dependency hierarchy:

  • mongo-express-1.0.0-alpha.4.tgz (Root Library)
    • json2csv-3.11.5.tgz
      • :x: lodash.set-4.3.2.tgz (Vulnerable Library)

This dependency chain illustrates how a vulnerability in a seemingly minor dependency can propagate through a project, ultimately affecting the security of the application as a whole. This highlights the importance of regularly scanning dependencies for vulnerabilities and applying necessary updates.

Affected Code Commit

The vulnerability was identified in the following commit: 58456d8a5755e9aff1d0e247b0796fb0e6a0c0f2. This commit serves as a specific point in the project's history where the vulnerable code was present. Examining the commit can provide further insights into the context of the vulnerability and how it might be exploited.

Vulnerability Details: Prototype Pollution

The core of CVE-2020-8203 lies in a prototype pollution vulnerability. To understand this, let's first define what prototype pollution is.

What is Prototype Pollution?

In JavaScript, every object inherits properties and methods from its prototype. The prototype is itself an object, and it can have its own prototype, creating a chain of inheritance. The topmost prototype in this chain is the Object.prototype, which is the ancestor of all JavaScript objects. Prototype pollution occurs when an attacker is able to modify the properties of Object.prototype (or any other prototype in the chain). Because all objects inherit from these prototypes, any changes made to a prototype will affect all objects that inherit from it. This can have far-reaching consequences, as it can lead to unexpected behavior, security vulnerabilities, and even complete application compromise.

How lodash.set is Vulnerable

The _.set method in lodash is designed to set a value at a specific path within an object. For example, _.set(obj, 'a.b.c', value) will set the value at obj.a.b.c. The vulnerability arises when the path provided to _.set is crafted in such a way that it modifies the prototype of an object rather than the object itself. This is often achieved by using special path segments like __proto__ or constructor.prototype, which are known ways to access and modify prototypes in JavaScript.

The _.zipObjectDeep method, which is used internally by _.set in certain scenarios, is also implicated in this vulnerability. This method is used to create an object from arrays of keys and values, and it can be exploited to pollute the prototype if the keys are maliciously crafted.

Impact of Prototype Pollution

The impact of prototype pollution can be significant. Some potential consequences include:

  • Denial of Service (DoS): By polluting the prototype with properties that cause errors or performance issues, an attacker can make the application unstable or unresponsive.
  • Information Disclosure: In some cases, prototype pollution can be used to leak sensitive information, such as internal application state or configuration details.
  • Remote Code Execution (RCE): In the most severe cases, prototype pollution can lead to RCE. This occurs when the attacker is able to inject malicious code into the application's execution context by manipulating the prototype. This could allow the attacker to take complete control of the server or the user's browser.

Technical Details: CVSS 3 Score

CVE-2020-8203 has been assigned a CVSS 3 score of 7.4, which is considered High severity. The CVSS (Common Vulnerability Scoring System) is a standardized way to assess the severity of software vulnerabilities. A score of 7.4 indicates a significant risk that should be addressed promptly.

CVSS 3 Metrics Breakdown

The CVSS 3 score is calculated based on a number of metrics, which can be broadly divided into Base Score Metrics, Exploitability Metrics, and Impact Metrics. Here's a breakdown of the metrics for CVE-2020-8203:

Exploitability Metrics:

  • Attack Vector: Network (AV:N): This means the vulnerability can be exploited over a network, making it accessible to remote attackers.
  • Attack Complexity: High (AC:H): The complexity of exploiting this vulnerability is high, meaning it requires specialized knowledge or techniques. However, once a working exploit is developed, it can be reused against other vulnerable systems.
  • Privileges Required: None (PR:N): No privileges are required to exploit this vulnerability. An attacker can exploit it without needing to authenticate or have any special permissions.
  • User Interaction: None (UI:N): No user interaction is required to exploit this vulnerability. The attacker can trigger the vulnerability without any action from the user.
  • Scope: Unchanged (S:U): An exploitation of the vulnerability affects a resource defined by the same security authority.

Impact Metrics:

  • Confidentiality Impact: None (C:N): There is no impact on confidentiality. The vulnerability does not allow the attacker to access sensitive information.
  • Integrity Impact: High (I:H): There is a high impact on integrity. The attacker can modify data or system configuration, potentially leading to incorrect behavior or system compromise.
  • Availability Impact: High (A:H): There is a high impact on availability. The attacker can cause a denial of service by making the system unstable or unresponsive.

For more information on CVSS3 Scores, you can visit the FIRST website.

Suggested Fix: Upgrade lodash

The recommended solution for CVE-2020-8203 is to upgrade to lodash version 4.17.20 or later. This version includes a fix that addresses the prototype pollution vulnerability. Upgrading lodash is a straightforward process that can be accomplished using a package manager like npm or yarn.

Upgrade Instructions

If you are using npm, you can upgrade lodash by running the following command in your project's root directory:

npm install lodash@4.17.20

If you are using yarn, you can use the following command:

yarn upgrade lodash@4.17.20

After running the upgrade command, it is important to verify that the correct version of lodash has been installed. You can do this by checking your package.json file or by running the following command:

npm list lodash

or

yarn list lodash

Additional Mitigation Steps

In addition to upgrading lodash, there are some other steps you can take to mitigate the risk of prototype pollution vulnerabilities:

  • Regularly Scan Dependencies: Use a vulnerability scanner to regularly check your project's dependencies for known vulnerabilities. This will help you identify and address potential security issues before they can be exploited.
  • Use Secure Coding Practices: Avoid using user-supplied input directly in object paths. Sanitize and validate input to prevent malicious data from being used to pollute prototypes.
  • Implement Prototype Freezing: In some cases, it may be possible to freeze the Object.prototype to prevent it from being modified. However, this may have compatibility issues with some libraries or frameworks.
  • Stay Informed: Keep up-to-date with the latest security advisories and best practices. This will help you stay ahead of potential threats and protect your applications.

Conclusion

CVE-2020-8203 is a significant vulnerability that highlights the importance of keeping your dependencies up-to-date and following secure coding practices. Prototype pollution vulnerabilities can have serious consequences, ranging from denial of service to remote code execution. By upgrading to lodash version 4.17.20 or later and implementing the additional mitigation steps outlined in this article, you can significantly reduce the risk of this vulnerability affecting your applications.

Remember to always prioritize security and stay proactive in protecting your systems from potential threats. Regularly scanning dependencies, using secure coding practices, and staying informed about the latest security advisories are essential steps in maintaining a secure software environment.

For further information on Open Source Security, consider exploring resources like the Mend platform, which offers comprehensive solutions for managing and securing open source dependencies. Additionally, staying updated with security best practices from trusted sources like OWASP can significantly enhance your application's security posture.