CVE-2023-0163 in Convict
Summary
by MITRE • 11/26/2024
Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') vulnerability in Mozilla Convict.
This allows an attacker to inject attributes that are used in other components, or to override existing attributes with ones that have incompatible type, which may lead to a crash.
The main use case of Convict is for handling server-side configurations written by the admins owning the servers, and not random users. So it's unlikely that an admin would deliberately sabotage their own server. Still, a situation can happen where an admin not knowledgeable about JavaScript could be tricked by an attacker into writing the malicious JavaScript code into some config files.
This issue affects Convict: before 6.2.4.
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Analysis
by VulDB Data Team • 10/15/2025
The CVE-2023-0163 vulnerability represents a prototype pollution flaw in Mozilla Convict, a configuration management library widely used for server-side configuration handling. This vulnerability falls under CWE-471, which specifically addresses the improper control of modifications to object prototype attributes. The issue stems from insufficient validation of input data when processing configuration parameters, allowing attackers to manipulate the prototype chain of objects within the application. When Convict processes configuration data, it fails to properly sanitize or validate attribute names that could potentially modify the Object.prototype directly, creating a dangerous attack vector that affects the entire JavaScript runtime environment.
The technical exploitation of this vulnerability occurs when an attacker can inject malicious configuration data that contains properties designed to modify prototype attributes. This allows attackers to inject new attributes into the prototype chain or override existing ones with incompatible types, leading to unpredictable behavior in the application. The vulnerability is particularly concerning because prototype pollution can cascade through the entire application, affecting other components that rely on the integrity of object prototypes. When an admin unknowingly incorporates malicious configuration data into server configurations, the prototype pollution can cause crashes, data corruption, or potentially enable further exploitation through chained vulnerabilities that leverage the polluted prototype chain.
The operational impact of CVE-2023-0163 extends beyond simple application instability, as it can create persistent security risks that persist across application sessions. Even though Convict is primarily designed for server-side configuration management by legitimate administrators, the vulnerability creates a scenario where social engineering attacks can be particularly effective. Attackers can trick administrators into including malicious JavaScript code in configuration files through various means such as phishing, compromised development environments, or supply chain attacks. The vulnerability's impact is amplified by the fact that prototype pollution can affect not just the specific component using Convict but can potentially compromise the entire application stack that depends on standard JavaScript object behavior. This makes the vulnerability particularly dangerous in environments where multiple components interact through shared object prototypes.
Mitigation strategies for CVE-2023-0163 focus on both immediate remediation and long-term architectural improvements. The most direct solution is upgrading to Convict version 6.2.4 or later, which includes proper input validation and prototype attribute sanitization. Organizations should also implement comprehensive configuration management practices, including code reviews of configuration files, automated scanning for suspicious patterns, and strict access controls for configuration files. Additional protective measures include implementing runtime checks that monitor for prototype modifications, using secure coding practices that prevent direct prototype manipulation, and establishing robust input validation at multiple layers of the application. From an ATT&CK perspective, this vulnerability relates to T1059.007 (Command and Scripting Interpreter: JavaScript) and T1566 (Phishing), as it can be exploited through both direct code injection and social engineering techniques. Organizations should also consider implementing application whitelisting and privilege separation to limit the potential impact of prototype pollution attacks, particularly in environments where configuration files might be processed with elevated privileges.