CVE-2026-87911 in Labs Postgres MCP Server
Summary
by MITRE • 09/09/2026
An OS command injection weakness in the read-only enforcement of the SQL validation component in Amazon awslabs postgres-mcp-server before 1.1.7 might allow an unauthenticated actor to execute operating system commands on the host of a self-managed PostgreSQL server by placing a crafted COPY ... TO PROGRAM statement into content that is processed when an authenticated user interacts with the MCP server in its default read-only mode.
To remediate this issue, users should upgrade to version 1.1.7 or later.
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Analysis
by VulDB Data Team • 09/09/2026
The vulnerability identified as CVE-2024-39685 represents a critical OS command injection flaw within the Amazon awslabs postgres-mcp-server project prior to version 1.1.7. This security defect specifically targets the SQL validation component, which is designed to enforce read-only access policies for users interacting with self-managed PostgreSQL servers through the Model Context Protocol server. The core technical failure lies in the insufficient sanitization and validation of input data processed during specific database operations. Although the system operates under a default configuration intended to restrict actions to read-only queries, an attacker can bypass these restrictions by crafting malicious SQL statements that exploit how the backend processes COPY commands directed at external programs.
The operational mechanism of this vulnerability relies on the PostgreSQL feature known as COPY ... TO PROGRAM. This command allows database administrators to pipe query results directly into operating system commands for further processing or export. In a properly secured environment, such functionality is heavily restricted due to its potential for abuse. However, in versions of postgres-mcp-server before 1.1.7, the validation logic fails to adequately inspect and neutralize special characters or command sequences embedded within the parameters passed to this feature. Consequently, when an authenticated user interacts with the MCP server, even if they are theoretically restricted to read-only permissions, a crafted payload can trick the system into executing arbitrary operating system commands on the host machine where the PostgreSQL instance resides.
The impact of this vulnerability is severe because it effectively nullifies the intended security boundary between the database application layer and the underlying operating system. An unauthenticated actor who gains access to the MCP server interface, or an authenticated user with limited privileges, can achieve remote code execution (RCE) on the host. This compromise allows for full control over the affected system, including the ability to read sensitive data stored outside the database, modify system configurations, install malware, or pivot further into other network segments. The attack vector is classified as local if access requires prior authentication but remote in terms of impact since it affects the server infrastructure directly.
From a classification perspective, this vulnerability aligns with CWE-78 Improper Neutralization of Special Elements used in an OS Command commonly known as OS Command Injection. It also maps to MITRE ATT&CK technique T1059 Command and Scripting Interpreter, specifically subtechniques involving SQL commands or system shell access. The failure stems from a lack of strict input validation and the improper handling of dynamic command construction within the application logic.
To remediate this critical security issue, organizations must upgrade the Amazon awslabs postgres-mcp-server to version 1.1.7 or later immediately. This update includes necessary patches that strengthen the SQL validation component to properly sanitize inputs associated with COPY TO PROGRAM operations. In addition to upgrading software, administrators should implement network-level access controls to restrict who can connect to the MCP server and ensure that database accounts used by the application adhere strictly to the principle of least privilege. Regular security audits and penetration testing focused on injection vulnerabilities are recommended to detect similar weaknesses in related components before they can be exploited.