Vulnerability in Modelcontextprotocol Rust-sdk
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 allo…
EPSS: 0.000 (0.4th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.
Affected products
- Modelcontextprotocol Rust-sdk — versions < 1.4.0
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC)
- security-advisories@github.com (x_refsource_CONFIRM)
Frequently asked questions
- What is CVE-2026-42559?
- CVE-2026-42559 is a high-severity vulnerability in Modelcontextprotocol Rust-sdk, classified under Origin Validation Error. CVSS score: 8.8/10. Published 2026-05-14.
- How severe is CVE-2026-42559?
- High severity. CVSS v3 base score is 8.8 out of 10.