VULNERABILITY INTELLIGENCE

CVE-2026-42559

CVSS score8.8 HIGH

EPSS probability0.27%

CISA KEVNot currently listed

Published2026-05-14

Last modified2026-10-26

Description

RMCP is an official Rust SDK for the Model Context Protocol. Prior to version 1.4.0, the rmcp crate's Streamable HTTP server transport (crates/rmcp/src/transport/streamable_http_server/) did not validate the incoming Host header. This allowed a malicious public website, via a DNS rebinding attack, to send authenticated requests to an MCP server running on the victim's loopback or private-network interface. This vulnerability is fixed in 1.4.0.