CVE Catalog

CVE-2026-42559

High
Published: Translated: NVD NIST

Summary

RMCP is an official Rust SDK for the Model Context Protocol. In versions prior to 1.4.0, the rmcp crate's Streamable HTTP server transport did not validate the Host header, allowing a malicious public website to send authenticated requests to an MCP server running on the victim's loopback or private-network interface via a DNS rebinding attack.

Risk Assessment

An attacker could exploit this vulnerability to gain control over the MCP server, potentially leading to data leakage or unauthorized access to network resources.

Recommendation

It is recommended to upgrade to version 1.4.0 or later to mitigate this vulnerability and implement additional protective measures such as HTTP header validation.

Related vulnerabilities

Original NVD description (English source)

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.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS