---
cve: "CVE-2026-42559"
severity: "HIGH"
cvss: 8.8
epss: "21%"
vendor: "modelcontextprotocol"
kev: false
exploited: false
published: "2026-05-14 15:16:46"
tags: [cve, security, high]
source: tsecurity.de CVE-Dossier
exported: "2026-09-08T10:27:18+02:00"
---

# CVE-2026-42559

> 8.8 HIGH · 🧪 PoC

## Beschreibung

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-Vektor

```
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Gering | bad |
| PR Privilegien | Keine | bad |
| UI Interaktion | Erforderlich | good |
| S Scope | Unverändert | good |
| C Vertraulichkeit | Hoch | bad |
| I Integrität | Hoch | bad |
| A Verfügbarkeit | Hoch | bad |

## Patch verfügbar (OSV)

- 8e22aa2de28df5a285eed87c11cd89bf15fa90d3 (Commit)

## Referenzen

- <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>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-42559) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_