In plain language
What this advisory means
A security issue was found in the Amazon awslabs postgres-mcp-server software before version 1.1.7. The software did not properly block certain malicious inputs in its SQL validation, which might allow someone without proper access to change data that should be read-only. Amazon fixed this in version 1.1.7 and recommends upgrading to protect your data.
Technical explanation
How the issue affects the environment
The vulnerability CVE-2026-85787 stems from an incomplete blocklist of disallowed SQL inputs in the validation component of the Amazon awslabs postgres-mcp-server prior to version 1.1.7. This flaw permits an unauthenticated attacker to inject crafted SQL commands into content submitted during interactions with the MCP server by authenticated users. Consequently, this can lead to unauthorized modification of data beyond the intended read-only scope. AWS recommends upgrading to version 1.1.7, which addresses this issue by enhancing the blocklist. Additionally, operating the MCP server under a minimal-privilege Postgres role enforces database-level access controls that limit exposure.
Operational impact
Why teams should care
If exploited, this vulnerability could allow unauthorized users to alter data that should be read-only, leading to potential data integrity issues, operational disruption, or violation of compliance policies. Organizations relying on the affected MCP server versions may face risks including unauthorized data modification and compromised trust in their systems.
Immediate action
Upgrade the awslabs postgres-mcp-server software to version 1.1.7 or later to incorporate the fix that properly validates SQL inputs and prevents unauthorized data modification. Also, ensure any forked or derivative code includes this patch.
Affected and fixed releases
Temporary risk reduction
Run the MCP server using a minimal-privilege Postgres role that has only the necessary permissions. Avoid connecting as superuser or roles with elevated privileges. For read-only usage, grant only CONNECT, USAGE, and SELECT privileges on needed schemas and enforce read-only transactions at the role level. For read/write usage, grant only the required INSERT, UPDATE, DELETE privileges scoped to specific schemas and tables. This database-level restriction complements application-level blocking, providing defense in depth.
Evidence and validation checklist
- AWS Security Bulletins page: https://aws.amazon.com/security/security-bulletins/rss/2026-101-aws/
- Bulletin ID: 2026-101-AWS published 09/04/2026
- Description of incomplete disallowed inputs in SQL validation
- Impact on awslabs postgres-mcp-server before version 1.1.7
- Resolution provided in version 1.1.7
- Recommendation to upgrade and use minimal-privilege Postgres roles
Authoritative reference
AWS Security Bulletins
QCS detected and normalized this record from the official source. Vendor guidance remains authoritative.