← back
CVE-2026-42559

RMCP: DNS rebinding vulnerability in rmcp Streamable HTTP server transport

CVSS 8.8 HIGHEPSS 0.2%CWE-346CWE-350
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.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Affected products
modelcontextprotocol · rust-sdk

Want to know if your infrastructure is exposed to this?

Talk to TrueHacking →
References
https://github.com/modelcontextprotocol/rust-sdk/commit/8e22aa2de28df5a285eed87c11cd89bf15fa90d3https://github.com/modelcontextprotocol/rust-sdk/issues/815https://github.com/modelcontextprotocol/rust-sdk/issues/822https://github.com/modelcontextprotocol/rust-sdk/pull/764https://github.com/modelcontextprotocol/rust-sdk/security/advisories/GHSA-89vp-x53w-74fx