CVE-2026-42559
RMCP: DNS rebinding vulnerability in rmcp Streamable HTTP server transport
- State
- Published
- Severity
- 8.8 High
- Published
- May 14, 2026
- Updated
- May 14, 2026
- Reserved
- Apr 28, 2026
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 3.1 | 8.8 High | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H | GitHub_M |
Weaknesses
Affected Products
| Product | Versions |
|---|---|
rust-sdkmodelcontextprotocol |
|
References
- https://github.com/modelcontextprotocol/rust-sdk/security/advisories/GHSA-89vp-x53w-74fx
- https://github.com/modelcontextprotocol/rust-sdk/issues/815
- https://github.com/modelcontextprotocol/rust-sdk/issues/822
- https://github.com/modelcontextprotocol/rust-sdk/pull/764
- https://github.com/modelcontextprotocol/rust-sdk/commit/8e22aa2de28df5a285eed87c11cd89bf15fa90d3
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