CVE-2020-7788: Ini Package Prototype Pollution Vulnerability

CVE-2020-7788 Overview

CVE-2020-7788 is a prototype pollution vulnerability affecting the npm ini package before version 1.3.6. When an application parses a maliciously crafted INI file using the ini.parse function, an attacker can pollute the prototype of JavaScript objects within the application. This type of vulnerability can lead to a wide range of security impacts depending on how the application handles the polluted objects, including remote code execution, denial of service, or unauthorized access to sensitive data.

Critical Impact

Prototype pollution in the ini package allows attackers to inject malicious properties into JavaScript object prototypes, potentially enabling remote code execution or application compromise in Node.js applications that parse untrusted INI files.

Affected Products

• ini_project ini (versions before 1.3.6)
• debian debian_linux 9.0

Discovery Timeline

• 2020-12-11 - CVE CVE-2020-7788 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2020-7788

Vulnerability Analysis

This vulnerability falls under CWE-1321 (Improperly Controlled Modification of Object Prototype Attributes), commonly known as prototype pollution. The ini package is a widely used npm library for parsing INI configuration files in Node.js applications.

The vulnerability exists in how the ini.parse function processes keys within INI files. When parsing specially crafted INI content containing keys like __proto__, the parser assigns values directly to the object prototype chain rather than treating them as regular properties. This allows an attacker to modify the behavior of all objects that inherit from the polluted prototype.

Prototype pollution attacks are particularly dangerous in JavaScript environments because they can affect all objects in an application. Depending on how the application uses the parsed configuration data, an attacker could potentially achieve remote code execution, bypass security controls, cause denial of service, or manipulate application logic.

Root Cause

The root cause lies in the ini.parse function's failure to properly sanitize or reject dangerous property names like __proto__, constructor, or prototype when processing INI file keys. The parser directly assigns values to object properties without checking whether these properties would modify the prototype chain.

When a key such as __proto__.polluted is encountered in an INI file, the parser traverses into the actual prototype object and sets properties on it, rather than creating a literal property named __proto__ on the target object. This allows an attacker to inject arbitrary properties into Object.prototype, which then become accessible on all objects in the application.

Attack Vector

The attack vector is network-based and requires no authentication or user interaction. An attacker can exploit this vulnerability by submitting a malicious INI file to any application that uses the vulnerable ini package to parse configuration data from untrusted sources.

The attacker crafts an INI file containing specially formatted keys that target the prototype chain. When the application parses this file, the malicious properties are injected into the JavaScript prototype hierarchy. The impact depends on the application context—for example, if the application later checks for the existence of specific properties on objects to make security decisions, the attacker-controlled prototype properties could influence those decisions.

For detailed technical analysis of this prototype pollution vulnerability, refer to the Snyk Vulnerability Report.

Detection Methods for CVE-2020-7788

Indicators of Compromise

• INI files containing suspicious keys such as __proto__, constructor, or prototype being submitted to or processed by the application
• Unexpected properties appearing on JavaScript objects that were not explicitly defined in application code
• Anomalous application behavior following the parsing of configuration files from external sources

Detection Strategies

• Implement npm audit scans in CI/CD pipelines to detect vulnerable versions of the ini package in dependencies
• Monitor application logs for errors or unexpected behavior following INI file parsing operations
• Use Software Composition Analysis (SCA) tools to inventory and track vulnerable ini package versions across the organization
• Deploy runtime application self-protection (RASP) to detect prototype pollution attempts

Monitoring Recommendations

• Enable dependency vulnerability scanning in package managers and container registries
• Monitor npm security advisories and automated dependency update services for alerts related to the ini package
• Implement file integrity monitoring for configuration files to detect unauthorized modifications
• Track package version usage across development and production environments to ensure patched versions are deployed

How to Mitigate CVE-2020-7788

Immediate Actions Required

• Upgrade the ini package to version 1.3.6 or later immediately across all affected applications
• Run npm audit or yarn audit to identify all projects using vulnerable versions of the ini package
• Review application code to identify where untrusted INI files may be parsed and prioritize those for immediate patching
• Consider temporarily blocking or sanitizing INI file uploads until the patch is deployed

Patch Information

The vulnerability has been addressed in ini package version 1.3.6. The fix is available via the GitHub commit. Users should update their package dependencies by running npm update ini or explicitly specifying "ini": ">=1.3.6" in their package.json file. Debian Linux 9.0 users should refer to the Debian LTS Announcement for distribution-specific patches.

Workarounds

• Avoid parsing INI files from untrusted or external sources until the package is updated
• Implement input validation to reject INI files containing dangerous keys like __proto__, constructor, or prototype
• Use Object.freeze(Object.prototype) as a defense-in-depth measure, though this may cause compatibility issues with some libraries
• Consider using alternative configuration parsers that include prototype pollution protections

# Upgrade ini package to patched version
npm update ini

# Or specify minimum safe version in package.json
npm install ini@">=1.3.6"

# Verify installed version
npm list ini