CVE-2026-85787 in postgres-mcp-server
Summary
by MITRE • 09/05/2026
An incomplete list of disallowed inputs in the SQL validation component in Amazon awslabs postgres-mcp-server before version 1.1.7 might allow an unauthenticated actor to modify data beyond the read-only scope by placing crafted SQL into the content that is submitted when an authenticated user interacts with the MCP server.
To remediate this issue, users should upgrade to version 1.1.7 or above.
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Analysis
by VulDB Data Team • 09/05/2026
The vulnerability identified in Amazon awslabs postgres-mcp-server prior to version 1.1.7 represents a critical failure in input validation within its SQL processing component. This flaw stems from an incomplete list of disallowed inputs, which effectively creates a gap in the security controls designed to sanitize user-supplied data before it is processed by the underlying database engine. In secure software architecture, particularly when dealing with dynamic query construction or execution, strict allow-listing or comprehensive deny-listing of malicious patterns is essential to prevent injection attacks. The absence of robust filtering mechanisms allows an attacker to bypass intended restrictions on SQL operations that should be limited to read-only access in certain contexts.
The technical nature of this flaw aligns closely with CWE-798, which describes the use of hardcoded credentials or insufficient input validation leading to privilege escalation, and more specifically CWE-89, known as SQL Injection. By failing to adequately sanitize inputs, the application permits an unauthenticated actor to inject crafted SQL statements into the content submitted during interactions with the MCP server. Although the initial interaction might appear to be authenticated by a legitimate user session or token, the vulnerability allows the attacker to manipulate the context of that request. The core issue lies in the server's inability to distinguish between benign and malicious SQL syntax when processing dynamic inputs, thereby enabling the execution of commands outside the intended scope.
The operational impact of this vulnerability is severe, as it permits an unauthenticated actor to modify data beyond the read-only scope assigned to them or expected by the application logic. This means that actions such as inserting, updating, or deleting records in the PostgreSQL database can be performed without proper authorization checks being enforced at the validation layer. Such unauthorized modifications compromise the integrity of the stored data and may lead to further exploitation vectors including data exfiltration or denial of service through destructive queries. From a threat modeling perspective, this behavior is consistent with ATT&CK technique T1059 Command and Scripting Interpreter via SQL commands, where attackers leverage database interfaces to execute arbitrary operations that undermine system integrity.
To mitigate the risks associated with this vulnerability, immediate action is required by upgrading the postgres-mcp-server software to version 1.1.7 or any subsequent release where these input validation gaps have been addressed. Developers and administrators should ensure that all instances of the affected component are patched promptly to restore proper access controls and data integrity protections. Additionally, implementing defense-in-depth strategies such as parameterized queries for dynamic SQL generation, enforcing least-privilege database accounts, and deploying web application firewalls can provide supplementary layers of security against similar injection-based attacks in future deployments.