CVE-2026-42559
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
- 8.8
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H - EPSS
- 0.3% chance of exploitation in the next 30 days; higher than 18% of CVEs (scores of 2026-10-25)
- CWEs
- CWE-346, CWE-350
- Published
- Modified
- Record from
- the NVD, synced
Packages (OSV)
| Advisory | Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|---|
| GHSA-89vp-x53w-74fx | crates.io | rmcp | <1.4.0 | 1.4.0 |
| GHSA-fvh2-gm75-j4j7 | crates.io | dynoxide-rs | >=0.9.3 <0.9.13 | 0.9.13 |
| GHSA-fvh2-gm75-j4j7 | npm | dynoxide | >=0.9.3 <0.9.13 | 0.9.13 |
| RUSTSEC-2026-0140 | crates.io | dynoxide-rs | >=0.9.3 <0.9.13 | 0.9.13 |
| RUSTSEC-2026-0189 | crates.io | rmcp | >=0.0.0-0 <1.4.0 | 1.4.0 |
References
- https://github.com/modelcontextprotocol/rust-sdk/commit/8e22aa2de28df5a285eed87c11cd89bf15fa90d3
- 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/security/advisories/GHSA-89vp-x53w-74fx