CVE-2026-18954 in DocumentDB MCP Server
Summary
by MITRE • 08/05/2026
Incorrect authorization in the aggregation pipeline tool in Amazon AWS Labs DocumentDB MCP Server before 1.0.12 might allow an authenticated MCP client to perform inappropriate write operations on the connected database via write-capable aggregation pipeline stages that bypass the read-only mode enforcement logic.
To remediate this issue, users should upgrade to version 1.0.12 or later.
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Analysis
by VulDB Data Team • 08/05/2026
This vulnerability represents a critical authorization flaw in Amazon Web Services DocumentDB Managed Cluster Protocol (MCP) server implementation prior to version 1.0.12. The security weakness stems from inadequate enforcement of read-only mode restrictions within the aggregation pipeline tool, creating a privilege escalation vector for authenticated attackers who can manipulate database operations through specific write-capable aggregation stages.
The technical exploitation occurs when an authenticated MCP client leverages certain aggregation pipeline stages that should be restricted to read-only operations. These stages bypass the intended security controls that normally enforce read-only mode enforcement logic, allowing malicious actors to execute unauthorized write operations against the connected database. This flaw directly violates the principle of least privilege and demonstrates a failure in access control mechanisms.
The operational impact of this vulnerability is significant as it enables authenticated users to perform inappropriate write operations that should be restricted. Attackers could potentially modify, delete, or insert data without proper authorization, leading to data integrity compromise, unauthorized modifications, and potential service disruption. The vulnerability affects all authenticated clients connected to DocumentDB instances running affected MCP server versions, making it particularly dangerous in environments with multiple legitimate users.
This issue maps to CWE-284 (Improper Access Control) and aligns with ATT&CK technique T1078 (Valid Accounts) and T1566 (Phishing). The vulnerability essentially allows attackers who have gained valid authentication credentials to escalate their privileges beyond what should be permitted. Organizations should implement immediate patch management procedures to upgrade to version 1.0.12 or later, which contains the necessary fixes for proper authorization enforcement in aggregation pipeline operations.
The root cause lies in insufficient validation of write capabilities within specific aggregation stages that should remain read-only during protected operations. This represents a classic case of inadequate input validation and access control implementation where the system fails to properly verify operation types against user permissions. Security teams should monitor for any unauthorized database modifications and review access logs for suspicious activity patterns that might indicate exploitation attempts.
Organizations using DocumentDB services should conduct immediate risk assessment to identify all affected systems running prior versions of the MCP server component, particularly those with high-value data or critical workloads where unauthorized write operations could cause significant operational impact. The remediation process requires careful planning to ensure minimal disruption while implementing the necessary version upgrade across all managed clusters.