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    CVE-2026-63118

    MCP Ruby SDK is the official Ruby SDK for Model Context Protocol servers and clients. Prior to 0.23.0, MCP::Server::Transports::StreamableHTTPTransport in the mcp gem does not validate the HTTP Host or Origin request headers, which allows a malicious browser page to use DNS rebinding to reach a locally running MCP server and invoke exposed tools. This issue is fixed in version 0.23.0.

    Published:Jul 29, 2026
    Last Modified:Jul 29, 2026
    EPS:Jul 29, 2026
    EPSS Score:
    CVSS Score:6.9

    Affected Products

    Vendor
    Modelcontextprotocol
    Product
    Ruby-sdk

    Exploits

    No exploit reference

    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