Helena Joyce
Prototype pollution is a vulnerability that can occur in JavaScript environments, where an attacker can modify the prototype of an object and affect all objects derived from it. This can lead to data theft, code execution, or denial of service attacks. Lodash, a JavaScript library, has been found to be vulnerable to prototype pollution attacks, specifically in the lodash.pick package. To fix this, it is recommended to upgrade to Lodash version 4.17.12 or higher, as the older versions are susceptible to prototype pollution attacks. This can be done using npm audit fix or npm audit fix --force, which will install a non-vulnerable version of Lodash. Additionally, other methods to prevent prototype pollution include freezing the prototype using Object.freeze, requiring schema validation of JSON input, and avoiding unsafe recursive merge functions.
| Characteristics | Values |
|---|---|
| Fix | Upgrade lodash to version 4.17.12 or higher |
| Use npm audit fix | |
| Use objects without prototypes, e.g. Object.create(null) | |
| Freeze the prototype with Object.freeze(Object.prototype) | |
| Require schema validation of JSON input | |
| Avoid using unsafe recursive merge functions | |
| Use Map instead of Object | |
| Keep libraries and systems up to date | |
| Conduct periodic application penetration testing | |
| Use the Server-Side Prototype Pollution Scanner extension for Burp Suite |
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What You'll Learn
Upgrade lodash to version 4.17.12 or higher
To address the issue of prototype pollution in lodash, it is recommended to upgrade to version 4.17.12 or higher. Prototype pollution is a vulnerability that affects JavaScript, allowing for the injection of properties into existing JavaScript language construct prototypes, such as objects.
Lodash, a modern JavaScript utility library, offers modularity, performance, and additional features. However, affected versions of this package are susceptible to prototype pollution through the set and setwith functions due to improper user input sanitization.
Upgrading to lodash version 4.17.12 or later addresses this security concern. This updated version includes patches to mitigate the prototype pollution vulnerability, ensuring that your application is protected from potential exploitation.
- Identify the current version of lodash in your project by checking the package.json file or running a dependency check.
- Compare the installed version with the latest available version of lodash. You can refer to the lodash change log or official documentation to identify the latest release.
- If your current version is older than 4.17.12, update to the latest version by running the appropriate package manager command, such as npm update lodash or yarn upgrade lodash.
- After the upgrade, rebuild and redeploy your application to ensure that the changes take effect.
By following these steps and upgrading to version 4.17.12 or higher, you can effectively mitigate the prototype pollution vulnerability in lodash and enhance the security of your JavaScript applications.
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Use Map instead of Object
To prevent prototype pollution in lodash, it is recommended to use Map instead of Object. Prototype pollution refers to the ability to inject properties into existing JavaScript language construct prototypes, such as objects. This vulnerability allows attackers to manipulate the prototype of 'Object' and introduce or modify properties that will affect all objects in the application.
Map is a data structure that can be used instead of objects to prevent prototype pollution attacks. It is a collection of key-value pairs, where each key is unique and can be used to access the associated value. Here are some reasons why using Map instead of Object can help prevent prototype pollution:
- Map has a different prototype chain: The prototype chain of Map is different from that of Object, which means that the properties and methods of Map are different from Object. This breaks the prototype chain and prevents pollution.
- Map is not susceptible to prototype pollution attacks: The Map data structure is not susceptible to prototype pollution attacks in the same way that Object is. This is because Map does not have the same magical attributes, such as __proto__, constructor, and prototype, that can be manipulated by attackers.
- Map provides a clear separation of concerns: By using Map instead of Object, developers can clearly separate the data and functionality of their application. This can make it easier to identify and prevent potential security vulnerabilities.
- Map is a built-in JavaScript feature: Map is a native feature of JavaScript, which means that it is widely supported and optimized for performance. This makes it a reliable choice for preventing prototype pollution in lodash.
Javascript
// Using Object (vulnerable to prototype pollution)
Const obj = {};
Obj.__proto__.pollutedProperty = "value"; // Injecting a property into the prototype
// Using Map (not vulnerable to prototype pollution)
Const map = new Map();
Map.set("key", "value"); // Adding a key-value pair to the Map
In the above example, the `obj` object is vulnerable to prototype pollution because the `__proto__` property can be manipulated to inject properties into the prototype. On the other hand, the `map` object is not susceptible to prototype pollution because it is a Map data structure that has a different prototype chain and does not have the same magical attributes as Object.
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Avoid unsafe recursive merge functions
Unsafe recursive merge functions can lead to prototype pollution in lodash. This occurs when a recursive merge is conducted on an empty object, allowing attackers to inject properties into existing JavaScript language construct prototypes, such as objects.
To avoid this vulnerability, it is recommended to freeze the prototype using Object.freeze(Object.prototype). This prevents any modifications to the prototype, making it immutable and safer from potential pollution.
Additionally, requiring schema validation of JSON input can help prevent unsafe recursive merge functions. By validating the input, you can ensure that it adheres to a predefined schema, reducing the risk of prototype pollution.
Another suggestion is to consider using objects without prototypes, such as Object.create(null). By breaking the prototype chain, you can prevent pollution from spreading through the prototype inheritance.
Upgrading to a safer version of lodash is also recommended. By upgrading to version 4.17.17 or higher, you can benefit from enhanced security measures that address prototype pollution vulnerabilities.
Finally, it is important to stay vigilant and keep your dependencies up to date. Regularly update your packages and apply patches to ensure you have the latest security fixes. This proactive approach helps protect against known vulnerabilities and strengthens the overall security posture of your applications.
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Patch old pull requests
Patching old pull requests is an important step in maintaining the security of your code. In the context of Lodash prototype pollution, here are some steps you can take to patch old pull requests:
- Upgrade Lodash: It is recommended to upgrade Lodash to version 4.17.17 or higher. This is because the affected versions of Lodash are vulnerable to prototype pollution due to improper user input sanitization. By upgrading, you benefit from improved modularity, performance, and security enhancements that address the prototype pollution vulnerability.
- Review and Apply Patches: Check for available patches and updates provided by the Lodash community. For example, Pull Request #4336 by Kirill89 addresses prototype pollution in _.defaultsDeep. Apply these patches to your codebase to fix the vulnerabilities.
- Fix Dependencies: Prototype pollution vulnerabilities can also arise from dependent packages. For instance, lodash.pick, a dependent package, has been reported to have a high severity prototype pollution vulnerability. Fix these dependencies by upgrading or applying specific patches provided by the community.
- Secure Your Environment: Implement security measures to protect your environment from prototype pollution attacks. Freeze the prototype using Object.freeze(Object.prototype), require schema validation of JSON input, and avoid unsafe recursive merge functions. These precautions will help prevent prototype pollution and enhance the overall security of your application.
- Validate and Test: After applying the patches, thoroughly validate and test your code to ensure that the fixes have been applied correctly. Use tools like Snyk to analyze your entire application and identify any remaining vulnerabilities. This step ensures that the patches effectively resolve the prototype pollution issue.
- Merge and Deploy: Once you have validated the patches, merge the changes into your main codebase and deploy the updated version. By deploying the patched version, you ensure that your application is protected against prototype pollution attacks and potential security breaches.
By following these steps, you can effectively patch old pull requests related to Lodash prototype pollution, enhancing the security and robustness of your codebase.
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Use the Server-Side Prototype Pollution Scanner extension
The Server-Side Prototype Pollution Scanner extension for Burp Suite helps automate the process of detecting prototype pollution vulnerabilities. Prototype pollution is a critical vulnerability in JavaScript applications that can lead to severe security risks.
- Install the Server-Side Prototype Pollution Scanner extension from the BApp Store and ensure it is enabled.
- Explore the target website using Burp's browser to map its content and accumulate traffic in the proxy history.
- Go to the Proxy > HTTP history tab in Burp and filter the list to show only in-scope items.
- Select all items in the list, right-click, and navigate to Extensions > Server-Side Prototype Pollution Scanner > Server-Side Prototype Pollution.
- Choose one of the scanning techniques from the list, such as Param scan, Param dot scan, or Param square scan.
- Modify the attack configuration if required, and then launch the scan.
- Review the results: In Burp Suite Professional, the extension reports any prototype pollution sources via the Issue Activity panel on the Dashboard and Target tabs. In the Community Edition, go to Extensions > Installed tab, select the extension, and monitor its Output tab.
This extension is a valuable tool for identifying server-side prototype pollution vulnerabilities, which can be challenging to detect without causing a Denial of Service (DoS). It helps to identify potential security risks and ensure the security of your JavaScript applications.
In addition to using the Server-Side Prototype Pollution Scanner extension, there are other measures to prevent prototype pollution in Lodash and other libraries. These include:
- Upgrading to Lodash version 4.17.17 or higher to address known prototype pollution vulnerabilities through the zipObjectDeep function.
- Validating user input, using secure object manipulation functions, and keeping dependencies up to date.
- Using objects without prototypes, such as Object.create(null), to break the prototype chain and prevent pollution.
- Employing Map data structures instead of objects to prevent prototype pollution attacks.
- Conducting periodic application penetration testing and maintaining up-to-date libraries and systems.
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Frequently asked questions
Prototype pollution is a vulnerability that occurs in JavaScript environments where an attacker can modify the prototype of an object, affecting all objects derived from it.
Attackers can modify the prototype of an object by injecting properties into existing JavaScript language construct prototypes, such as objects. This can lead to data theft, code execution, or denial of service attacks.
To prevent prototype pollution in Lodash, you can:
- Upgrade Lodash to version 4.17.12 or higher.
- Freeze the prototype using Object.freeze(Object.prototype).
- Require schema validation of JSON input.
- Avoid using unsafe recursive merge functions.
- Use objects without prototypes, such as Object.create(null).
All versions of the Lodash library for NodeJS below 4.17.12 are vulnerable to prototype pollution attacks.
To fix prototype pollution in Lodash, you can use npm audit fix, which will suggest downgrading to a safer version. Additionally, you can use tools like the Server-Side Prototype Pollution Scanner extension for Burp Suite to identify and address prototype pollution vulnerabilities.
