CVE-2026-42559
High · 8.8CVSS
8.8
EPSS
0.2%
Published
May 14, 2026
CISA due date
—
The record
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.
Affected packages
| Ecosystem | Package | Introduced | Fixed |
|---|---|---|---|
| crates.io | dynoxide-rs | 0.9.3 | 0.9.13 |
| crates.io | rmcp | 0 | 1.4.0 |
| npm | dynoxide | 0.9.3 | 0.9.13 |
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