CVE-2021-23807 in jsonpointer
Summary
by MITRE • 11/03/2021
This affects the package jsonpointer before 5.0.0. A type confusion vulnerability can lead to a bypass of a previous Prototype Pollution fix when the pointer components are arrays.
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Analysis
by VulDB Data Team • 03/05/2025
The vulnerability identified as CVE-2021-23807 affects the jsonpointer package version 5.0.0 and earlier, representing a critical type confusion issue that undermines previous security measures. This flaw specifically targets the package's handling of pointer components when they are arrays, creating a pathway for attackers to bypass existing prototype pollution mitigations. The vulnerability resides in the package's inability to properly validate data types during pointer resolution operations, allowing malicious input to manipulate object prototypes in unintended ways.
This type confusion vulnerability operates at the core of how jsonpointer processes array-based path components, where the package fails to maintain proper type checking between different data structures during traversal operations. When array components are present in jsonpointer paths, the system incorrectly handles type transitions that should be strictly enforced, enabling attackers to craft inputs that exploit the gap between expected and actual data types. The flaw essentially allows attackers to manipulate the prototype chain of objects through carefully constructed array paths, which can lead to arbitrary code execution or data manipulation in applications that rely on this package for json path resolution.
The operational impact of CVE-2021-23807 extends beyond simple prototype pollution, as it specifically targets the integrity of existing security controls designed to prevent such vulnerabilities. Applications using vulnerable versions of jsonpointer are susceptible to attackers who can bypass previously implemented protections by leveraging array-based pointer components that the package fails to properly sanitize. This vulnerability affects any system where jsonpointer is used for processing user input or external data, particularly in web applications, api gateways, or any service that processes json paths from untrusted sources. The bypass capability makes this vulnerability particularly dangerous as it can undermine the effectiveness of security measures that were specifically designed to address prototype pollution threats.
Security mitigations for this vulnerability require immediate upgrade to jsonpointer version 5.0.0 or later, which includes proper type validation and handling of array components in pointer paths. Organizations should also implement input validation measures at application layers to prevent malicious json pointer structures from reaching the vulnerable package. Additionally, regular security audits of dependency trees should include checks for similar type confusion vulnerabilities that might exist in other json processing libraries. This vulnerability aligns with CWE-129 and CWE-1319 categories related to improper input validation and type confusion issues, and represents a technique that could be classified under ATT&CK tactic TA0043 (Persistence) when exploited for maintaining access through prototype manipulation. The remediation process should include comprehensive testing to ensure that existing prototype pollution protections are not compromised by the upgrade process, as well as monitoring for potential exploitation attempts in production environments.