MySQL MCP Server: Missing Origin/Host Validation in SSE Transport Enables Unauthenticated SQL Execution

What happened

• In SSE mode, the server built its SSE transport without the security settings, so the SDK's protection against DNS rebinding was off. [1]
• The app had no CORS or TrustedHost middleware, and all three routes (/, /sse, /messages/) had no login. [1]
• The service listened on 0.0.0.0 by default, which means every network interface. [1]
• This only happens when MCP_TRANSPORT=sse; the default stdio mode is not affected. [1]

Impact

• An attacker on the network could run any SQL query without credentials. [1]
• They could take out and change all data in the configured database. [1]
• If the MySQL account has FILE privilege, they could read and write files, which can lead to running their own code. [1]

What was done

• The maintainers released version 0.4.2. [1]
• In 0.4.2, DNS-rebinding protection is turned on by passing TransportSecuritySettings(enable_dns_rebinding_protection=True) to SseServerTransport. [1]
• The documented recommended bind address is 127.0.0.1. [1]

Sources

1. GHSA-rqfv-2mw9-78g2 — GitHub Advisory Database

Every statement above was checked against these sources before publishing. Spotted an error? Tell us and we will correct it with a dated note.