CVE-2026-42559

RMCP: DNS rebinding vulnerability in rmcp Streamable HTTP server transport

Published May 14, 2026 CVSS 3.1 · 8.8 High EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

Sign in to view the affected projects.

Advisories

Source ID Title
Github GHSA Github GHSA GHSA-89vp-x53w-74fx rmcp Streamable HTTP server transport has a DNS rebinding vulnerability
History
Type Values Removed Values Added
First Time appeared Modelcontextprotocol
Modelcontextprotocol rust-sdk
Vendors & Products Modelcontextprotocol
Modelcontextprotocol rust-sdk
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
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.
Title RMCP: DNS rebinding vulnerability in rmcp Streamable HTTP server transport
Weaknesses CWE-346
CWE-350
References
Metrics cvssV3_1

{'score': 8.8, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
May 14, 2026, 4:00 PM
Reserved
Apr 28, 2026, 4:56 PM
Status
Deferred
Published
May 14, 2026, 3:16 PM
Modified
Oct 26, 2026, 2:10 PM