CVE-2026-33498 in parse-server
Summary
by MITRE • 03/24/2026
Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Prior to versions 8.6.55 and 9.6.0-alpha.44, an attacker can send an unauthenticated HTTP request with a deeply nested query containing logical operators to permanently hang the Parse Server process. The server becomes completely unresponsive and must be manually restarted. This is a bypass of the fix for CVE-2026-32944. This issue has been patched in versions 8.6.55 and 9.6.0-alpha.44.
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Analysis
by VulDB Data Team • 03/29/2026
The vulnerability described in CVE-2026-33498 represents a critical denial of service condition affecting Parse Server versions prior to 8.6.55 and 9.6.0-alpha.44. This issue exploits a fundamental flaw in the query parsing mechanism that allows attackers to craft malicious HTTP requests containing deeply nested queries with logical operators. The vulnerability specifically targets the server's ability to process complex query structures, leading to a complete system hang that requires manual intervention for recovery. This represents a significant operational risk as the affected systems become completely unresponsive and cannot process any further legitimate requests until restarted manually.
The technical implementation of this vulnerability leverages the server's query processing logic to create resource exhaustion through malformed requests. When an attacker submits an HTTP request containing a deeply nested query structure with logical operators such as $or, $and, or other complex conditional expressions, the Parse Server's query parser enters an infinite loop or becomes trapped in a resource-intensive processing state. This occurs because the server's query validation and parsing mechanisms fail to properly handle extreme nesting levels or complex logical combinations that could potentially cause stack overflow conditions or excessive CPU consumption. The vulnerability specifically bypasses previous mitigation efforts implemented for CVE-2026-32944, indicating that the fix for the earlier issue was incomplete or insufficient in addressing all possible query construction patterns that could lead to similar resource exhaustion scenarios.
From an operational impact perspective, this vulnerability creates a severe availability risk for any system running affected Parse Server versions. The permanent hanging of the server process means that legitimate users and applications cannot access the backend services, resulting in complete service disruption. The requirement for manual restart operations creates additional operational overhead and potential downtime for affected organizations. This vulnerability particularly affects systems that rely heavily on Parse Server for backend operations, including mobile applications, web services, and other systems that depend on the Parse Server's data processing capabilities. The attack vector is particularly concerning because it requires no authentication, meaning any external party can potentially exploit this vulnerability to disrupt services.
The mitigation strategy for this vulnerability involves immediate deployment of patches to versions 8.6.55 and 9.6.0-alpha.44, which contain the necessary fixes to prevent the query parsing logic from entering problematic states. Organizations should implement comprehensive monitoring to detect unusual query patterns and establish automated alerting for potential exploitation attempts. The fix addresses the underlying parsing logic to properly validate and limit the depth and complexity of nested queries, preventing the server from becoming unresponsive during query processing. This aligns with security best practices for preventing resource exhaustion attacks and demonstrates the importance of proper input validation and query sanitization in backend services. The vulnerability classification aligns with CWE-400 which addresses unspecified resource exhaustion, and may also relate to ATT&CK technique T1499.004 for network denial of service attacks through resource exhaustion. Organizations should also consider implementing rate limiting and query complexity monitoring as additional defensive measures to prevent similar issues from occurring in other parts of their infrastructure.