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OpenAdvisories
High · 8.8 Public exploit CVE-2026-42559 EUVD-2026-30292GHSA-89vp-x53w-74fxGHSA-fvh2-gm75-j4j7RUSTSEC-2026-0140RUSTSEC-2026-0189

RMCP: DNS rebinding vulnerability in rmcp Streamable HTTP server transport

Published May 14, 2026 · Updated May 14, 2026 · Assigned by GitHub_M

Vendor: Model Context Protocol Product: rust-sdk Package: dynoxide Package: dynoxide-rs Package: nushell Package: rmcp Package: zed Ecosystem: crates.io Ecosystem: npm Ecosystem: Wolfi

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.

Affected products

VendorProductAffectedFixed
modelcontextprotocol rust-sdk < 1.4.0 —

Fixed in Linux distributions

Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.

Wolfi

ReleasePackageFixed inAdvisory
Wolfi rolling nushell 0.112.2-r3 —
Wolfi rolling zed 1.2.6-r1 —

Public exploits

Exploit or proof-of-concept code for this vulnerability is publicly available, which lowers the bar for attackers. Treat it as a reason to patch sooner.

Third-party code, not reviewed by us. Public PoCs are sometimes fake or contain malware. Read the code first and run it only in an isolated lab, against systems you are authorised to test.

GitHub 1 repository

  • joaovicdev/EXPLOIT-CVE-2026-42559 ★ 0 · Sep 6, 2026

    Docker lab + Python PoC for CVE-2026-42559 - DNS rebinding via unvalidated Host header in the rmcp (Rust MCP SDK) Streamable HTTP server transport

Sources: PoC-in-GitHub, Metasploit Framework, Exploit-DB — updated daily. Only links are listed; no exploit code is hosted here.

Affected packages

EcosystemPackageAffectedFixedRecord
crates.io dynoxide-rs >= 0.9.3, < 0.9.13 0.9.13 GHSA-fvh2-gm75-j4j7
crates.io rmcp < 1.4.0 1.4.0 GHSA-89vp-x53w-74fx
crates.io rmcp >= 0.0.0-0, < 1.4.0 1.4.0 RUSTSEC-2026-0189
npm dynoxide >= 0.9.3, < 0.9.13 0.9.13 GHSA-fvh2-gm75-j4j7

References