CVE-2020-8237 in json-bigint
Summary
by MITRE
Prototype pollution in json-bigint npm package < 1.0.0 may lead to a denial-of-service (DoS) attack.
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Analysis
by VulDB Data Team • 09/19/2020
The vulnerability identified as CVE-2020-8237 represents a critical prototype pollution flaw within the json-bigint npm package version 1.0.0 and earlier. This security weakness stems from improper handling of object prototype properties during JSON parsing operations, creating a pathway for malicious actors to manipulate the prototype chain of objects. The vulnerability specifically affects applications that rely on the json-bigint library for processing large numbers in JSON format, making it particularly dangerous in environments where data integrity and system stability are paramount. The issue manifests when the library processes JSON data containing maliciously crafted keys that can pollute the Object.prototype, thereby affecting all objects in the JavaScript runtime environment. This type of vulnerability falls under the CWE-471 category of "Modification of Assumed-Immutable Data" and represents a classic prototype pollution attack vector that has been documented in numerous security advisories across the industry.
The technical exploitation of this vulnerability occurs when an attacker crafts JSON input containing properties that match prototype methods or properties, causing the library to inadvertently modify the global Object.prototype. When the json-bigint library processes such input, it fails to properly sanitize or validate the keys being used, leading to the pollution of prototype properties with attacker-controlled values. This pollution can result in various security implications including but not limited to denial-of-service conditions, where the application becomes unstable or unresponsive due to the corrupted prototype chain. The vulnerability is particularly concerning because it can be exploited through simple JSON parsing operations, making it accessible to attackers with minimal technical expertise. The prototype pollution can cause applications to behave unpredictably, potentially leading to crashes, memory exhaustion, or other stability issues that directly translate to denial-of-service conditions. The attack vector is straightforward yet effective, requiring only that the vulnerable application processes untrusted JSON input through the affected library.
The operational impact of CVE-2020-8237 extends beyond simple service disruption to potentially compromise entire application ecosystems that depend on the json-bigint package. Organizations using vulnerable versions of this library face significant risks including system instability, performance degradation, and potential data corruption when processing JSON data. The vulnerability is especially dangerous in server-side applications where JSON parsing is a common operation, as it can be exploited through various attack vectors including web applications, APIs, and backend services. When exploited successfully, the prototype pollution can lead to cascading failures throughout the application stack, affecting multiple components that rely on object prototypes for their operation. The DoS conditions resulting from this vulnerability can be particularly challenging to detect and remediate, as they may not immediately manifest during normal application operation but can be triggered by specific JSON input patterns. This makes the vulnerability particularly insidious in production environments where the full attack surface may not be immediately apparent.
Mitigation strategies for CVE-2020-8237 require immediate action to upgrade the json-bigint package to version 1.0.0 or later, which contains the necessary patches to prevent prototype pollution. Organizations should conduct comprehensive audits of their dependency trees to identify all applications and services that rely on vulnerable versions of the library, implementing a coordinated remediation approach across their infrastructure. Security teams should also consider implementing input validation and sanitization measures at multiple layers of their applications to provide defense-in-depth against similar vulnerabilities. The recommended solution aligns with ATT&CK technique T1210 for exploitation of weaknesses in software libraries, emphasizing the importance of maintaining up-to-date dependencies and implementing proper security controls. Additional protective measures include monitoring application behavior for unusual prototype modifications, implementing strict content validation for JSON inputs, and establishing automated dependency scanning processes to detect vulnerable components before they can be exploited. Organizations should also consider implementing application-level protections such as prototype freezing or object sealing to prevent unauthorized modifications to prototype properties, providing an additional layer of defense against prototype pollution attacks.