CVE-2026-42559

{
  "id": "CVE-2026-42559",
  "sourceIdentifier": "[email protected]",
  "published": "2026-05-14T15:16:46.750",
  "lastModified": "2026-10-26T14:10:00.130",
  "vulnStatus": "Deferred",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "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."
    },
    {
      "lang": "es",
      "value": "RMCP es un SDK oficial de Rust para el Protocolo de Contexto del Modelo. Antes de la versión 1.4.0, el transporte de servidor HTTP Streamable del crate rmcp (crates/rmcp/src/transport/streamable_http_server/) no validaba el encabezado Host entrante. Esto permitía que un sitio web público malicioso, a través de un ataque de DNS rebinding, enviara solicitudes autenticadas a un servidor MCP ejecutándose en la interfaz de loopback o de red privada de la víctima. Esta vulnerabilidad está corregida en la versión 1.4.0."
    }
  ],
  "affected": [
    {
      "source": "[email protected]",
      "affectedData": [
        {
          "vendor": "modelcontextprotocol",
          "product": "rust-sdk",
          "versions": [
            {
              "version": "< 1.4.0",
              "status": "affected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {
    "cvssMetricV31": [
      {
        "source": "[email protected]",
        "type": "Secondary",
        "cvssData": {
          "version": "3.1",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H",
          "baseScore": 8.8,
          "baseSeverity": "HIGH",
          "attackVector": "NETWORK",
          "attackComplexity": "LOW",
          "privilegesRequired": "NONE",
          "userInteraction": "REQUIRED",
          "scope": "UNCHANGED",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "availabilityImpact": "HIGH"
        },
        "exploitabilityScore": 2.8,
        "impactScore": 5.9
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "timestamp": "2026-05-14T16:00:22.834947Z",
          "id": "CVE-2026-42559",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "role": "CISA Coordinator",
          "version": "2.0.3"
        }
      }
    ]
  },
  "weaknesses": [
    {
      "source": "[email protected]",
      "type": "Secondary",
      "description": [
        {
          "lang": "en",
          "value": "CWE-346"
        },
        {
          "lang": "en",
          "value": "CWE-350"
        }
      ]
    }
  ],
  "references": [
    {
      "url": "https://github.com/modelcontextprotocol/rust-sdk/commit/8e22aa2de28df5a285eed87c11cd89bf15fa90d3",
      "source": "[email protected]"
    },
    {
      "url": "https://github.com/modelcontextprotocol/rust-sdk/issues/815",
      "source": "[email protected]"
    },
    {
      "url": "https://github.com/modelcontextprotocol/rust-sdk/issues/822",
      "source": "[email protected]"
    },
    {
      "url": "https://github.com/modelcontextprotocol/rust-sdk/pull/764",
      "source": "[email protected]"
    },
    {
      "url": "https://github.com/modelcontextprotocol/rust-sdk/security/advisories/GHSA-89vp-x53w-74fx",
      "source": "[email protected]"
    }
  ]
}