CVE-2020-8268 in json8-merge-patch Package
Summary
by MITRE • 11/09/2020
Prototype pollution vulnerability in json8-merge-patch npm package < 1.0.3 may allow attackers to inject or modify methods and properties of the global object constructor.
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Analysis
by VulDB Data Team • 12/04/2020
The CVE-2020-8268 vulnerability represents a critical prototype pollution flaw within the json8-merge-patch npm package version 1.0.2 and earlier. This vulnerability stems from improper input validation during the merge patch operation where untrusted data can manipulate the prototype chain of JavaScript objects. The flaw occurs when the package processes JSON merge patch operations without adequately sanitizing or validating the input structure, allowing attackers to inject malicious properties into the Object prototype. This type of vulnerability falls under the CWE-471 category of "Modification of Assumed-Immutable Data" and specifically manifests as a prototype pollution attack vector that can have far-reaching consequences across applications using vulnerable versions of the package.
The technical exploitation of this vulnerability involves crafting malicious JSON data that when processed through the merge patch functionality can alter the behavior of core JavaScript objects. Attackers can inject properties or methods into the Object.prototype constructor, which then propagates to all objects that inherit from it throughout the application's runtime environment. This pollution can occur through various attack vectors including user input, API responses, or any external data source that gets processed by the vulnerable package. The vulnerability is particularly dangerous because it can enable attackers to manipulate core JavaScript functionality, potentially leading to arbitrary code execution or bypass of security controls. The ATT&CK framework categorizes this as a privilege escalation technique under T1068, where attackers leverage code injection vulnerabilities to gain elevated privileges within the application context.
The operational impact of CVE-2020-8268 extends beyond simple data manipulation as it can compromise the integrity and confidentiality of applications relying on vulnerable versions of the json8-merge-patch package. Applications using this package may experience unexpected behavior, denial of service conditions, or more severe consequences such as complete system compromise if the prototype pollution leads to code execution. The vulnerability affects any application that processes external JSON data through the merge patch functionality, making it particularly dangerous in web applications, microservices architectures, or any environment where untrusted data is processed. Security teams must consider the potential for cascading effects as prototype pollution can propagate through the entire object hierarchy, affecting multiple components that depend on standard JavaScript object behavior.
Mitigation strategies for CVE-2020-8268 require immediate action to upgrade the json8-merge-patch package to version 1.0.3 or later, which includes proper input validation and prototype sanitization measures. Organizations should also implement comprehensive dependency scanning and monitoring to identify other vulnerable packages within their ecosystems. Additional protective measures include implementing strict input validation at multiple layers, using secure coding practices such as avoiding direct prototype manipulation, and employing runtime protections like prototype lockdown mechanisms. The vulnerability demonstrates the importance of secure package management and regular security auditing of third-party dependencies, as highlighted in industry best practices for secure software development lifecycle. Security professionals should also consider implementing automated vulnerability scanning tools and establishing dependency hygiene policies to prevent similar issues in the future.