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CVE-2026-59971criticalBroken access control2026-09-15

CVE-2026-59971: MySQL MCP Server in SSE mode runs anyone's SQL, including via DNS rebinding

Before 0.4.2, mysql-mcp-server with MCP_TRANSPORT=sse binds to 0.0.0.0 with no authentication and no DNS rebinding protection. A network attacker, or a malicious web page through the victim's browser, can call execute_sql against the database.

01.

What it is

Setting MCP_TRANSPORT=sse makes src/mysql_mcp_server/server.py build SseServerTransport without security_settings or enable_dns_rebinding_protection. The Starlette routes /, /sse and /messages/ have no authentication, and the service binds to 0.0.0.0 by default.

A network attacker can reach the execute_sql tool directly, or use DNS rebinding so a victim's browser relays requests to a locally bound server, and run queries with the configured MySQL user's rights.

02.

How to check

  1. Affected: mysql-mcp-server (PyPI) before 0.4.2 when run with MCP_TRANSPORT=sse.
  2. The default stdio transport isn't affected by this issue.
03.

How to fix

  1. Upgrade mysql-mcp-server to 0.4.2 or later.
  2. Give the MCP server a MySQL user with the least privileges it needs, and don't expose the SSE port to other networks.
pip show mysql-mcp-server | grep -i version
04.

Sources

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