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CVE-2026-88257

Estado: AplazadaMedia (5.3)—

Vulnerabilidad de validación incorrecta de entradas en BeamMCP.Schema en ScriptKittyOS beam_mcp que permite a un cliente MCP llegar a la función de despacho de una herramienta con argumentos que infringen el esquema de entrada anunciado por el servidor. BeamMCP.Schema.validate/2 comprobaba type, required, additionalProperties, enum y los límites numéricos únicamente en el objeto de argumentos de nivel superior.

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Las restricciones dentro de objetos anidados y en los elementos de arrays (items, minItems, maxItems, minLength, maxLength, pattern, required anidado, enum y additionalProperties: false) se anunciaban en tools/list y nunca se comprobaban en tools/call ni en prompts/get, y las palabras clave fuera del subconjunto aplicado (oneOf, anyOf, $ref) se anunciaban y se ignoraban.

Un host cuyo código de despacho confía en el esquema que declaró recibe valores que el esquema prohíbe, como un número fuera de rango o una clave no declarada dentro de un objeto anidado. Lo que el host haga con dicho valor determina el impacto.

Este problema afecta a beam_mcp: desde 0.1.0 antes de 0.10.1.

Traducción automática del texto original de NVD (en inglés).

CVSS

Probabilidad de explotación (EPSS)

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

🎯 Técnicas ATT&CK

Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.

Inferido por reglas deterministas a partir del vector CVSS y la CWE. Solo orientativo.

🛡️ Mitigaciones ATT&CK que cubren estas técnicas

Vulnerability ScanningThreat Intelligence ProgramPrivileged Account ManagementNetwork SegmentationDisable or Remove Feature or ProgramApplication Isolation and Sandboxing

Tecnologías afectadas (1)

⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.

Scriptkit — Beam MCPAI

CWE

Referencias

JSON original (NVD)

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{
  "id": "CVE-2026-88257",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-88257",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-10-08T13:59:14.866448Z"
        }
      }
    ],
    "cvssMetricV40": [
      {
        "type": "Secondary",
        "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
        "cvssData": {
          "Safety": "NOT_DEFINED",
          "version": "4.0",
          "Recovery": "NOT_DEFINED",
          "baseScore": 5.3,
          "Automatable": "NOT_DEFINED",
          "attackVector": "NETWORK",
          "baseSeverity": "MEDIUM",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
          "exploitMaturity": "NOT_DEFINED",
          "providerUrgency": "NOT_DEFINED",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "attackRequirements": "NONE",
          "privilegesRequired": "LOW",
          "subIntegrityImpact": "NONE",
          "vulnIntegrityImpact": "LOW",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "subAvailabilityImpact": "NONE",
          "vulnAvailabilityImpact": "NONE",
          "availabilityRequirement": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "subConfidentialityImpact": "NONE",
          "vulnConfidentialityImpact": "NONE",
          "confidentialityRequirement": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "vulnerabilityResponseEffort": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED"
        }
      }
    ]
  },
  "affected": [
    {
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "affectedData": [
        {
          "cpes": [
            "cpe:2.3:a:scriptkittyos:beam_mcp:*:*:*:*:*:*:*:*"
          ],
          "repo": "https://github.com/ScriptKittyOS/beam_mcp",
          "vendor": "ScriptKittyOS",
          "modules": [
            "'Elixir.BeamMCP.Schema'",
            "'Elixir.BeamMCP.Server'"
          ],
          "product": "beam_mcp",
          "versions": [
            {
              "status": "affected",
              "version": "0.1.0",
              "lessThan": "0.10.1",
              "versionType": "semver"
            }
          ],
          "packageURL": "pkg:hex/beam_mcp",
          "packageName": "beam_mcp",
          "programFiles": [
            "lib/beam_mcp/schema.ex",
            "lib/beam_mcp/server.ex"
          ],
          "collectionURL": "https://repo.hex.pm",
          "defaultStatus": "unaffected",
          "programRoutines": [
            {
              "name": "'Elixir.BeamMCP.Schema':validate/2"
            },
            {
              "name": "'Elixir.BeamMCP.Server':handle_message/2"
            }
          ]
        },
        {
          "cpes": [
            "cpe:2.3:a:scriptkittyos:beam_mcp:*:*:*:*:*:*:*:*"
          ],
          "repo": "https://github.com/ScriptKittyOS/beam_mcp",
          "vendor": "ScriptKittyOS",
          "modules": [
            "'Elixir.BeamMCP.Schema'",
            "'Elixir.BeamMCP.Server'"
          ],
          "product": "beam_mcp",
          "versions": [
            {
              "status": "affected",
              "version": "083838eb8e17fe5f6fcaf761bdbe203110288b0b",
              "lessThan": "289dbdbad641943b29a3b8d1eb36506cc8cec10a",
              "versionType": "git"
            }
          ],
          "packageURL": "pkg:github/scriptkittyos/beam_mcp",
          "packageName": "scriptkittyos/beam_mcp",
          "programFiles": [
            "lib/beam_mcp/schema.ex",
            "lib/beam_mcp/server.ex"
          ],
          "collectionURL": "https://github.com",
          "defaultStatus": "unaffected",
          "programRoutines": [
            {
              "name": "'Elixir.BeamMCP.Schema':validate/2"
            },
            {
              "name": "'Elixir.BeamMCP.Server':handle_message/2"
            }
          ]
        }
      ]
    }
  ],
  "published": "2026-10-08T14:17:01.613",
  "references": [
    {
      "url": "https://cna.erlef.org/cves/CVE-2026-88257.html",
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
    },
    {
      "url": "https://github.com/ScriptKittyOS/beam_mcp/commit/083838eb8e17fe5f6fcaf761bdbe203110288b0b",
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
    },
    {
      "url": "https://github.com/ScriptKittyOS/beam_mcp/commit/289dbdbad641943b29a3b8d1eb36506cc8cec10a",
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
    },
    {
      "url": "https://github.com/ScriptKittyOS/beam_mcp/security/advisories/GHSA-mrg2-4747-fmpw",
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
    },
    {
      "url": "https://osv.dev/vulnerability/EEF-CVE-2026-88257",
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
    }
  ],
  "vulnStatus": "Deferred",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "description": [
        {
          "lang": "en",
          "value": "CWE-20"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "Improper Input Validation vulnerability in BeamMCP.Schema in ScriptKittyOS beam_mcp allows an MCP client to reach a tool's dispatch function with arguments that violate the input schema the server advertised. BeamMCP.Schema.validate/2 checked type, required, additionalProperties, enum and numeric bounds on the top-level arguments object only. Constraints inside nested objects and on array items (items, minItems, maxItems, minLength, maxLength, pattern, nested required, enum and additionalProperties: false) were advertised by tools/list and never checked at tools/call or prompts/get, and keywords outside the enforced subset (oneOf, anyOf, $ref) were advertised and ignored.\n\nA host whose dispatch code relies on the schema it declared receives values the schema forbids, such as an out-of-range number or an undeclared key inside a nested object. What the host does with such a value decides the impact.\n\nThis issue affects beam_mcp: from 0.1.0 before 0.10.1."
    }
  ],
  "lastModified": "2026-10-08T21:01:07.830",
  "sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
}