Mcp Go
Monthly
DNS rebinding in mcp-go before 0.56.0 allows a malicious webpage to bypass localhost isolation and invoke tools or read resources on a victim's locally-running MCP server. Both StreamableHTTPServer and SSEServer accepted loopback connections without validating the Host header, and the SSE transport's permissive default CORS policy removed an additional browser-level barrier. No public exploit has been identified and no CISA KEV listing exists, but the attack is practical for any developer running an affected server while browsing the web.
DNS rebinding in mcp-go before 0.56.0 allows a malicious webpage to bypass localhost isolation and invoke tools or read resources on a victim's locally-running MCP server. Both StreamableHTTPServer and SSEServer accepted loopback connections without validating the Host header, and the SSE transport's permissive default CORS policy removed an additional browser-level barrier. No public exploit has been identified and no CISA KEV listing exists, but the attack is practical for any developer running an affected server while browsing the web.