Vulnerability Report

CVE-2026-42559

Title: DNS Rebinding Attack in rmcp Streamable HTTP server transport

Other

Proof Of Concept

PoC Available for CVE-2026-42559

CWE Category CWE-346
Published Date May 14, 2026
Modified Date May 14, 2026
Exploit Status Available
Score 8.8 CVSS v3.1
Exploit Probability (EPSS)
0.24%

Vulnerability Summary

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.

Impacted Vendors

Analysis in Progress...

Reference Links

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
CVSS v3.1
Source Entity [email protected]
Severity HIGH
8.8
Attack Vector
NETWORK
Complexity
LOW
Privileges
N/A
Interaction
REQUIRED
Confidentiality
N/A
Integrity
N/A
Availability
N/A
Scope
UNCHANGED
RAW VECTOR CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Associated Attack Patterns (CAPEC)

Total: Patterns

CVE-2026-42559 Exploits & PoCs (Proof Of Concept)

GitHub https://github.com/joaovicdev/EXPLOIT-CVE-2026-42559
View Code
MODIFIED

Vulnerability data updated via NVD.

MODIFIED

Vulnerability data updated via NVD.

Attack Vector Matrix

Access Vector NETWORK
Complexity LOW
Privileges N/A
Interaction REQUIRED
CVSS Vector String CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Affected Stack

No specific products linked.