CVE-2026-18699 in MongoDB
Summary
by MITRE • 08/11/2026
An issue in MongoDB Server's query planner could allow an authenticated user with read-level privileges to cause the server process to terminate unexpectedly by submitting a specially formed query against a collection with a text index. This could result in a denial of service, affecting connected clients and in-flight operations.
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Analysis
by VulDB Data Team • 08/11/2026
This vulnerability resides within the MongoDB query planning mechanism, specifically when processing queries against collections that utilize text indexes. The flaw represents a denial of service condition that can be exploited by authenticated users possessing read-level permissions, demonstrating a critical weakness in the server's resource management and error handling capabilities. The issue manifests when a maliciously crafted query is executed against a text-indexed collection, causing the MongoDB server process to abruptly terminate and restart.
The technical root cause stems from insufficient input validation and memory management within the query planner component of MongoDB Server. When processing certain text search operations, particularly those involving complex text index queries, the system fails to properly handle malformed or specially constructed query parameters that trigger unexpected behavior in the underlying execution engine. This vulnerability aligns with CWE-691, which addresses insufficient control flow management in software systems, and represents a classic example of how improper error handling can lead to service interruption rather than graceful degradation.
The operational impact of this vulnerability extends beyond simple service disruption as it affects all connected clients and ongoing database operations during the server restart cycle. Clients experiencing active connections may lose their sessions and must reestablish database connectivity, potentially causing application downtime or performance degradation. In production environments with high transaction volumes or applications requiring persistent connections, this vulnerability could result in significant business impact including data access delays and potential loss of service availability.
Organizations should implement immediate mitigations including applying the latest security patches released by MongoDB, which typically address the specific query planning logic that causes the process termination. Network segmentation and privilege management should be reviewed to limit access to text-indexed collections for users who do not require such functionality. Monitoring systems should be enhanced to detect unusual query patterns or service restarts that might indicate exploitation attempts. Additionally, implementing proper input validation at the application layer can provide an additional defense-in-depth mechanism against malformed queries reaching the database server directly. This vulnerability demonstrates the importance of comprehensive testing for edge cases in database query processing and highlights the need for robust error handling mechanisms that prevent process termination under normal operational conditions rather than allowing system instability to occur.