Improper Prototype Pollution in Mingo

Executive Summary

CVE-2026-15698 is a prototype pollution vulnerability in the kofrasa mingo library, affecting versions up to 7.2.1. The vulnerability occurs in the Update API functions (update/updateOne/updateMany) when manipulating the argument 'Set'.

Prototype pollution is a type of attack where an attacker exploits the ability to modify the prototype of a base object (like Object.prototype) in JavaScript. This can lead to unexpected behavior in applications that rely on object properties or methods.

• The vulnerability allows remote attackers to manipulate object prototype attributes by using dangerous path segments like '__proto__' in update operations.
• The issue arises because the $set operator in update operations follows these dangerous path segments without proper validation, leading to prototype pollution.

The fix for this vulnerability was introduced in version 7.2.2, which includes validation to prevent the use of '__proto__' in selector paths and ensures safer object property access.

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Detection Guidance

Detecting this vulnerability requires checking if your system or application uses the affected versions of the mingo library (up to 7.2.1) and if it processes user-controlled update documents or paths in the `mingo/updater` module. Since this is a prototype pollution vulnerability, you can look for signs of exploitation or misconfiguration in your JavaScript environment.

• Check the installed version of the mingo library in your project. If it is version 7.2.1 or earlier, it is vulnerable. You can do this by inspecting the `package.json` file or running: `npm list mingo` or `yarn list mingo`.
• Review your application code for usage of the `update`, `updateOne`, or `updateMany` functions in the mingo library, particularly where the `$set` operator is used with user-controlled input. Look for paths containing `__proto__`, `constructor`, or `prototype` in update operations.
• Monitor for unexpected behavior in your application, such as newly created objects inheriting unexpected properties or functions. This could indicate prototype pollution.
• Use static analysis tools or security scanners that detect prototype pollution vulnerabilities in JavaScript code. Tools like `eslint-plugin-security` or `snyk` may help identify risky patterns.

There are no direct network-based detection methods for this vulnerability, as it is a code-level issue. Focus on code audits and dependency checks.

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Impact Analysis

This vulnerability can impact you in several ways if your application uses the affected versions of the mingo library (up to 7.2.1) and relies on user-controlled update documents or paths.

• Prototype pollution can lead to logic bypass, where security checks or application logic are circumvented due to unexpected properties being added to objects.
• It can enable property injection, where attackers inject malicious properties into objects, potentially altering application behavior.
• Denial of service (DoS) attacks may occur if the pollution causes the application to crash or become unresponsive.
• Secondary security issues may arise, such as privilege escalation or data corruption, depending on how the application uses the affected objects.

The impact is particularly severe if your application processes untrusted input in update operations, as attackers can exploit this to manipulate the prototype chain of JavaScript objects.

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Compliance Impact

This vulnerability can affect compliance with common standards and regulations in the following ways:

• GDPR (General Data Protection Regulation): If the vulnerability leads to unauthorized access or manipulation of personal data, it could violate GDPR's requirements for data protection and integrity. Prototype pollution might enable attackers to bypass security controls, leading to data breaches or unauthorized data modifications, which could result in non-compliance with GDPR's data protection principles.
• HIPAA (Health Insurance Portability and Accountability Act): For applications handling protected health information (PHI), this vulnerability could compromise the confidentiality, integrity, or availability of PHI. If prototype pollution leads to unauthorized access or data corruption, it may violate HIPAA's security and privacy rules, resulting in non-compliance.
• Other standards (e.g., ISO 27001, SOC 2): The vulnerability undermines security controls related to data integrity and access management. Non-compliance with these standards may occur if the vulnerability is not addressed, as it could lead to security incidents that violate requirements for secure data handling and risk management.

To maintain compliance, it is critical to upgrade to the patched version (7.2.2) and ensure that all user-controlled inputs are properly validated and sanitized to prevent exploitation of this vulnerability.

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Mitigation Strategies

To mitigate this vulnerability, follow these immediate steps:

• Upgrade the mingo library to version 7.2.2 or later. This version includes the fix for the prototype pollution vulnerability. You can upgrade using npm or yarn: `npm install [email protected]` or `yarn add [email protected]`.
• If upgrading is not immediately possible, apply the patch manually by incorporating the changes from the commit `fadc398251792c2ba441cbc539f359fc7943c0c2`. This includes adding validation to reject dangerous path segments like `__proto__`, `constructor`, and `prototype` in update operations.
• Review and sanitize all user-controlled input used in update operations, particularly those involving the `$set` operator. Ensure that no user input can manipulate object prototypes.
• Implement input validation to block or escape dangerous path segments (e.g., `__proto__`, `constructor`, `prototype`) before they are processed by the mingo library.
• Monitor your application for any unexpected behavior or newly created objects with inherited properties, which could indicate ongoing exploitation attempts.

After applying the fix, test your application thoroughly to ensure that legitimate update operations continue to work as expected and that no new issues are introduced.

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