Parse Server is an open-source backend framework that runs on Node.js and is widely used for building application backends. In versions prior to 9.5.2-alpha.6 and 8.6.19, there exists an improper access control vulnerability (CWE-284) identified as CVE-2026-30962. The root cause is that the server's validation logic for protected fields only examines the top-level keys in query requests. When a query constraint on a protected field is nested inside a logical operator (such as $or, $and), the validation check is bypassed entirely. This means that authenticated users can craft queries that circumvent the intended restrictions on protected fields, allowing them to retrieve sensitive data that should be inaccessible. Since all default parse-server deployments define protected fields, this vulnerability broadly impacts deployments using affected versions. The vulnerability has a CVSS 4.0 base score of 7.1, reflecting high severity due to network attack vector, low attack complexity, no privileges required beyond authentication, and no user interaction needed. The vulnerability does not affect confidentiality, integrity, or availability beyond unauthorized data disclosure (confidentiality impact is high). No known exploits have been reported in the wild as of the publication date. The issue is resolved in parse-server versions 9.5.2-alpha.6 and 8.6.19 by improving the validation logic to correctly inspect nested query constraints. Organizations running vulnerable versions should upgrade immediately and review access control policies for sensitive data fields.

This vulnerability allows any authenticated user to bypass access controls on protected fields by manipulating query structures, leading to unauthorized disclosure of sensitive data. The impact is primarily on confidentiality, as attackers can extract data that should be restricted. This can lead to data breaches, loss of user privacy, and potential compliance violations depending on the nature of the exposed data. Since parse-server is often used as a backend for mobile and web applications, sensitive user information, internal metadata, or business-critical data could be exposed. The ease of exploitation is high due to low attack complexity and no need for elevated privileges beyond authentication. The scope is broad because all default deployments with affected versions are vulnerable. Although no integrity or availability impacts are noted, the confidentiality breach alone can have severe reputational and regulatory consequences for organizations worldwide.

The primary mitigation is to upgrade parse-server to version 9.5.2-alpha.6 or 8.6.19 or later, where the vulnerability is fixed. Until upgrades can be applied, organizations should implement strict query validation and sanitization on the application side to detect and block nested logical operators targeting protected fields. Additionally, review and minimize the number of protected fields and sensitive data stored in parse-server to reduce exposure. Implement robust authentication and monitoring to detect unusual query patterns indicative of exploitation attempts. Employ network segmentation and least privilege principles to limit access to parse-server instances. Conduct regular security audits and penetration testing focusing on query injection and access control bypass scenarios. Finally, educate developers and administrators about this vulnerability and ensure timely patch management processes are in place.