Varonis: DNS Rebinding Is a Protocol-Level MCP Flaw — Three CVEs Confirm Same Fundamental Weakness Across Implementations

Varonis Blog·high signal

Varonis published a technical analysis showing DNS rebinding is a systemic MCP attack pattern, not isolated to individual implementations. Three separate CVEs (Java SDK, Apollo, Azure) independently confirm the same root cause: MCP's HTTP transport lacks mandatory origin validation by design. The analysis demonstrates the attack chain from malicious DNS response through browser pivot to unauthorized localhost MCP tool invocation.