CVE-2026-42559HIGH 8.8EPSS p11.5%
CVE-2026-42559CVE-2026-42559
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.
Scoring
| CVSS 3.1 | 8.8 (HIGH) |
| Vector | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H |
| EPSS | 0.21% probability of exploitation · percentile 11.5% · 2026-06-18T12:00:27Z |
| Published | 2026-05-14 |
| Last modified | 2026-05-14 |
Underlying weaknesses· 2
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
2
| Type | Target | Confidence | Tier |
|---|---|---|---|
| Weakness | Origin Validation Errorcwe-346 | 0% | live |
| Weakness | Reliance on Reverse DNS Resolution for a Security-Critical Actioncwe-350 | 0% | live |
Related by meaning· 6
Nearest entities by semantic similarity across the cs-graph corpus.