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    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.

    Published:May 14, 2026
    Last Modified:May 17, 2026
    EPS:May 14, 2026
    EPSS Score:0.00018
    CVSS Score:8.8

    Affected Products

    Vendor
    Modelcontextprotocol
    Product
    Rust-sdk

    Exploits

    https://github.com/joaovicdev/CVE-2026-42559https://github.com/joaovicdev/EXPLOIT-CVE-2026-42559

    Common Attack Pattern Enumeration and Classification (CAPEC)

    CAPEC-111 JSON Hijacking (aka JavaScript Hijacking)
    CAPEC-141 Cache Poisoning
    CAPEC-142 DNS Cache Poisoning
    CAPEC-160 Exploit Script-Based APIs
    CAPEC-21 Exploitation of Trusted Identifiers
    CAPEC-275 DNS Rebinding
    CAPEC-384 Application API Message Manipulation via Man-in-the-Middle
    CAPEC-385 Transaction or Event Tampering via Application API Manipulation
    CAPEC-386 Application API Navigation Remapping
    CAPEC-387 Navigation Remapping To Propagate Malicious Content
    CAPEC-388 Application API Button Hijacking
    CAPEC-510 SaaS User Request Forgery
    CAPEC-59 Session Credential Falsification through Prediction
    CAPEC-60 Reusing Session IDs (aka Session Replay)
    CAPEC-73 User-Controlled Filename
    CAPEC-75 Manipulating Writeable Configuration Files
    CAPEC-76 Manipulating Web Input to File System Calls
    CAPEC-89 Pharming

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High