CVE-2026-18704 in MongoDB
Summary
by MITRE • 08/11/2026
An issue in MongoDB Server's aggregation framework could allow an authenticated user with only read privileges to perform write operations against collections they should not be able to modify. This is due to an internal-use aggregation stage being reachable by external clients without an appropriate authorization check on its embedded operations.
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Analysis
by VulDB Data Team • 08/11/2026
This vulnerability represents a critical authorization bypass flaw within MongoDB Server's aggregation framework that undermines the principle of least privilege and could enable unauthorized data modification by authenticated users with minimal permissions. The issue stems from an internal aggregation stage that was inadvertently exposed to external client connections without proper authorization validation, creating a pathway for malicious actors to execute write operations against collections they should not have access to. This represents a fundamental breakdown in MongoDB's access control mechanisms where the system fails to properly validate whether a user has appropriate permissions before executing potentially destructive operations. The vulnerability specifically affects scenarios where users with read-only privileges attempt to leverage this exposed internal stage during aggregation pipeline execution, allowing them to manipulate data in collections they should only be able to read from.
The technical flaw manifests through improper authorization checks within MongoDB's internal aggregation pipeline processing, where certain stages designed for internal system use are accessible to external clients without appropriate permission validation. This creates a situation where legitimate read-only users can invoke operations that should be restricted to administrators or users with write privileges. The vulnerability operates at the intersection of privilege escalation and access control enforcement, where the system's authorization model fails to properly validate operation types against user permissions during aggregation pipeline execution. According to CWE-285, this represents an improper authorization issue where the system does not adequately verify that a user has sufficient privileges for the requested operations. The flaw essentially allows authenticated users to bypass normal access controls by leveraging internal system components that were never intended to be exposed to external client requests.
The operational impact of this vulnerability is significant as it enables authenticated attackers with minimal privileges to perform write operations including insert, update, and delete actions against collections they should not have access to. This creates potential data integrity issues where unauthorized modifications can occur without proper audit trails or authorization logging. The vulnerability affects MongoDB deployments where aggregation pipelines are used extensively, particularly in environments where multiple user roles exist and strict separation of privileges is required. Attackers could exploit this by crafting specific aggregation pipelines that utilize the vulnerable internal stage, potentially leading to data corruption, information disclosure, or denial of service conditions. This issue directly impacts compliance with security frameworks like NIST SP 800-53 which emphasizes the importance of access control and privilege management in database systems.
Security mitigation strategies should focus on immediate patching of affected MongoDB versions and implementation of network-level restrictions to limit client access to aggregation endpoints. Organizations should review their user permission models and ensure that read-only users cannot inadvertently access internal system components through aggregation pipelines. Network segmentation and firewall rules can help reduce exposure by limiting direct connections to MongoDB's aggregation framework from untrusted networks. Additionally, implementing comprehensive logging and monitoring of aggregation pipeline operations can help detect unauthorized usage patterns. The fix typically involves ensuring proper authorization checks are enforced before executing any operation within the aggregation framework, particularly for internal stages that should remain inaccessible to external clients. This vulnerability highlights the importance of defense in depth strategies and proper input validation in database systems, aligning with ATT&CK technique T1078 which covers valid accounts and privilege escalation through unauthorized access to system components. Regular security assessments and code reviews should be conducted to identify similar exposure points within database systems to prevent future incidents of this nature.