The security bulletin identifies CVE-2026-85787 as an incomplete list of disallowed inputs in the SQL validation component of Amazon awslabs postgres-mcp-server before version 1.1.7. It explains that an unauthenticated actor might modify data beyond the read-only scope by placing crafted SQL into content submitted during an authenticated user interaction with the MCP server.
IMPACT AND PATCH PATH
Impacted versions: any pypi package version < 1.1.7. This issue has been addressed in version 1.1.7. Operators are advised to upgrade and patch any forked or derivative code to include the fixes.
MITIGATIONS AND OPERATIONAL GUIDANCE
Upgrade to the patched version (1.1.7) and patch derivative code as needed.
Run the MCP server as a minimal-privilege Postgres role to ensure the database enforces boundaries regardless of SQL that reaches it.
Do not connect using a superuser, rds_superuser, or cluster master user since those roles bypass row-level security and can access credential catalogs or terminate sessions.
For read-only access, grant CONNECT + USAGE + SELECT on only the necessary schemas and force read-only transactions at the role level.
For read/write access, grant only the specific INSERT/UPDATE/DELETE privileges required, scoped to the necessary schemas and tables.
DEFENSE-IN-DEPTH INTERPRETATION
Combining a minimal-privilege role (database-enforced) with the blocklist (application-enforced) provides defense in depth: even if a query slips past the blocklist, the role's privileges bound what it can do. Ashwak N is acknowledged for reporting this issue as part of the coordinated disclosure process.
UNCERTAINTY AND WHAT TO MONITOR NEXT
The bulletin does not provide quantitative risk metrics or empirical testing results, and no further details are provided beyond the mitigations listed. Operators should stay alert for any follow-up advisories or CVE updates.
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