CVE-2025-64718: Fix Prototype Pollution In Js-yaml

by Alex Johnson 51 views

This article details the medium severity vulnerability, CVE-2025-64718, detected in versions 3.14.1 and 4.1.0 of the js-yaml library. This vulnerability, discovered by pustovitDmytro and reported via node-package-tester, highlights a critical prototype pollution issue that can impact applications parsing YAML documents.

Vulnerability Details

The vulnerability resides within the js-yaml library, a popular JavaScript YAML parser and serializer. Specifically, versions 3.14.1 and 4.1.0 are susceptible to prototype pollution attacks. An attacker can manipulate the prototype of a parsed YAML document by exploiting the __proto__ property. This allows them to inject or modify properties on all JavaScript objects, potentially leading to denial of service, information disclosure, or even remote code execution under specific conditions. This can occur when parsing untrusted YAML documents, making it crucial to address this vulnerability promptly. Prototype pollution is a type of security vulnerability that arises when an attacker is able to manipulate the __proto__ property of JavaScript objects. This property allows direct access to the object's prototype, and by modifying it, an attacker can inject or modify properties on all objects that inherit from that prototype. This can have a wide range of security implications, including denial of service, information disclosure, and even remote code execution. In the context of js-yaml, the vulnerability allows an attacker to inject or modify properties on the Object.prototype, which is the base prototype for all JavaScript objects. This means that any object created in the application could be affected by the attacker's modifications. The impact of this vulnerability depends on how the application uses the parsed YAML data. If the application uses the data to configure itself or to perform other sensitive operations, the attacker could potentially gain control of the application. For example, an attacker could inject a malicious function into the Object.prototype that would be executed whenever a new object is created. This function could then be used to steal sensitive data, modify the application's behavior, or even execute arbitrary code on the server. Addressing this vulnerability is crucial to protect your application from potential attacks. Upgrading to the patched version of js-yaml is the recommended solution, as it eliminates the possibility of prototype pollution. Additionally, implementing security measures such as input validation and sanitization can further reduce the risk of exploitation.

Impact

The impact of CVE-2025-64718 can be significant. By exploiting this vulnerability, attackers can potentially:

  • Modify application behavior: Inject malicious properties into JavaScript objects, leading to unexpected or harmful actions.
  • Cause denial of service: Overload the application with injected properties, making it unresponsive.
  • Expose sensitive information: Access and steal sensitive data stored in JavaScript objects.
  • Achieve remote code execution (in specific scenarios): Under certain conditions, an attacker could execute arbitrary code on the server.

The severity of this vulnerability is rated as Medium, with a CVSS 3 score of 5.3. While the confidentiality and availability impacts are none, the integrity impact is low, indicating that an attacker could modify data but not completely compromise the system. The exploitability metrics show that the attack vector is network-based, with low complexity, no privileges required, and no user interaction needed, making it easier for attackers to exploit. Prototype pollution vulnerabilities, like the one in js-yaml, can have a significant impact on the security of web applications. These vulnerabilities allow attackers to inject or modify properties on JavaScript objects, potentially leading to a variety of malicious outcomes. One of the primary impacts of prototype pollution is the ability to modify application behavior. By injecting malicious properties into JavaScript objects, attackers can alter the way the application functions, leading to unexpected or harmful actions. For example, an attacker could inject a property that redirects users to a phishing site or that modifies the application's data in a way that benefits the attacker. In addition to modifying application behavior, prototype pollution can also lead to denial of service (DoS) attacks. By overloading the application with injected properties, attackers can make it unresponsive and unavailable to legitimate users. This can be particularly damaging for applications that rely on high availability, such as e-commerce sites or online banking platforms. Furthermore, prototype pollution can expose sensitive information. By accessing and stealing sensitive data stored in JavaScript objects, attackers can gain access to confidential information such as user credentials, financial data, and personal information. This information can then be used for identity theft, fraud, or other malicious purposes. In some specific scenarios, prototype pollution can even lead to remote code execution (RCE). This occurs when an attacker is able to inject code into the application that is then executed by the server. RCE is the most severe type of security vulnerability, as it allows attackers to gain complete control of the affected system. To mitigate the risks associated with prototype pollution vulnerabilities, developers should take steps to protect their applications. This includes using secure coding practices, such as input validation and sanitization, and keeping dependencies up to date with the latest security patches. Additionally, developers should consider using tools that can automatically detect and prevent prototype pollution attacks.

Technical Details: CVSS 3 Score

  • Base Score: 5.3 (Medium)
  • Exploitability Metrics:
    • Attack Vector: Network (AV:N)
    • Attack Complexity: Low (AC:L)
    • Privileges Required: None (PR:N)
    • User Interaction: None (UI:N)
    • Scope: Unchanged (S:U)
  • Impact Metrics:
    • Confidentiality Impact: None (C:N)
    • Integrity Impact: Low (I:L)
    • Availability Impact: None (A:N)

For more information on CVSS3 Scores, refer to the CVSS 3.0 Calculator.

Remediation

The recommended solution is to upgrade js-yaml to version 4.1.1 or later. This version includes a patch that resolves the prototype pollution vulnerability. If upgrading js-yaml directly is not feasible, consider upgrading dependencies that rely on js-yaml. For example, upgrading eslint to version 8.9.0 or later will also resolve the vulnerability, as it includes a patched version of js-yaml. The urgency to address prototype pollution vulnerabilities stems from their ability to compromise the integrity and security of applications. Unlike vulnerabilities that may only affect specific parts of an application, prototype pollution can have widespread consequences due to the nature of JavaScript's prototype inheritance model. When an attacker successfully pollutes the prototype of a JavaScript object, they can inject or modify properties that are inherited by all objects created from that prototype. This means that the attacker's modifications can potentially affect the entire application, leading to a variety of malicious outcomes. One of the primary reasons to address prototype pollution vulnerabilities promptly is to prevent the modification of application behavior. By injecting malicious properties into JavaScript objects, attackers can alter the way the application functions, leading to unexpected or harmful actions. For example, an attacker could inject a property that redirects users to a phishing site or that modifies the application's data in a way that benefits the attacker. Another important reason to address prototype pollution vulnerabilities promptly is to prevent denial of service (DoS) attacks. By overloading the application with injected properties, attackers can make it unresponsive and unavailable to legitimate users. This can be particularly damaging for applications that rely on high availability, such as e-commerce sites or online banking platforms. Furthermore, prototype pollution can expose sensitive information. By accessing and stealing sensitive data stored in JavaScript objects, attackers can gain access to confidential information such as user credentials, financial data, and personal information. This information can then be used for identity theft, fraud, or other malicious purposes. In some specific scenarios, prototype pollution can even lead to remote code execution (RCE). This occurs when an attacker is able to inject code into the application that is then executed by the server. RCE is the most severe type of security vulnerability, as it allows attackers to gain complete control of the affected system. Addressing prototype pollution vulnerabilities promptly is crucial to protect your application from potential attacks. By upgrading to the latest version of affected libraries and implementing secure coding practices, you can significantly reduce the risk of exploitation and ensure the security of your application.

Conclusion

The CVE-2025-64718 vulnerability in js-yaml poses a significant risk due to the potential for prototype pollution. It is highly recommended to upgrade to version 4.1.1 or later, or to upgrade dependent packages like eslint to version 8.9.0 or later, to mitigate this risk. Regularly monitoring and updating your dependencies is crucial for maintaining the security of your applications. Ignoring vulnerabilities like CVE-2025-64718 can have serious consequences, potentially leading to data breaches, service disruptions, and reputational damage. By proactively addressing these issues, you can significantly reduce the risk of exploitation and ensure the security of your application. One of the key benefits of proactively addressing vulnerabilities is the prevention of data breaches. Data breaches can have significant financial and reputational consequences for organizations. By addressing vulnerabilities like CVE-2025-64718, you can reduce the risk of attackers gaining access to sensitive data and prevent costly data breaches. In addition to preventing data breaches, proactively addressing vulnerabilities can also help to avoid service disruptions. Service disruptions can have a significant impact on businesses, particularly those that rely on online services. By addressing vulnerabilities that could lead to service disruptions, you can ensure that your services remain available to your customers and avoid potential revenue losses. Furthermore, proactively addressing vulnerabilities can help to protect your organization's reputation. A security breach can damage an organization's reputation and erode customer trust. By demonstrating a commitment to security and proactively addressing vulnerabilities, you can build trust with your customers and protect your organization's reputation. Regular monitoring and updating of dependencies is essential for maintaining the security of your applications. By staying informed about the latest security threats and promptly addressing vulnerabilities, you can significantly reduce the risk of exploitation and ensure the long-term security of your applications. In conclusion, proactively addressing vulnerabilities like CVE-2025-64718 is crucial for maintaining the security of your applications and protecting your organization from potential risks. By taking a proactive approach to security, you can prevent data breaches, service disruptions, and reputational damage, and ensure the long-term success of your organization.

For more information on YAML security best practices, visit the OWASP YAML Vulnerabilities page.

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