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CVE-2026-1664

Estado: AplazadaMedia (6.9)—

Summary

An Insecure Direct Object Reference has been found to exist in `createHeaderBasedEmailResolver()` function within the Cloudflare Agents SDK. The issue occurs because the `Message-ID` and `References` headers are parsed to derive the target agentName and agentId without proper validation or origin checks, allowing an external attacker with control of these headers to route inbound mail to arbitrary Durable Object instances and namespaces .

Root cause

The `createHeaderBasedEmailResolver()` function lacks cryptographic verification or origin validation for the headers used in the routing logic, effectively allowing external input to dictate internal object routing.

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Impact

Insecure Direct Object Reference (IDOR) in email routing lets an attacker steer inbound mail to arbitrary Agent instances via spoofed Message-ID.

Mitigation:

Detalles técnicos trazas, registros y código del informe original
  *  PR:  https://github.com/cloudflare/agents/blob/main/docs/email.md ] provides the necessary architectural context for coding agents to mitigate the issue by refactoring the resolver to enforce strict identity boundaries.
  *  Agents-sdk users should  upgrade to agents@0.3.7

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).

Tecnologías afectadas (1)

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

Cloudflare — Agents SDKAI

CWE

Referencias

JSON original (NVD)

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{
  "id": "CVE-2026-1664",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-1664",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-02-03T14:38:24.747542Z"
        }
      }
    ],
    "cvssMetricV40": [
      {
        "type": "Secondary",
        "source": "cna@cloudflare.com",
        "cvssData": {
          "Safety": "NOT_DEFINED",
          "version": "4.0",
          "Recovery": "NOT_DEFINED",
          "baseScore": 6.9,
          "Automatable": "NOT_DEFINED",
          "attackVector": "NETWORK",
          "baseSeverity": "MEDIUM",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:L/SI:L/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": "NONE",
          "subIntegrityImpact": "LOW",
          "vulnIntegrityImpact": "LOW",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "subAvailabilityImpact": "NONE",
          "vulnAvailabilityImpact": "NONE",
          "availabilityRequirement": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "subConfidentialityImpact": "LOW",
          "vulnConfidentialityImpact": "LOW",
          "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": "cna@cloudflare.com",
      "affectedData": [
        {
          "repo": "https://github.com/cloudflare/agents",
          "versions": [
            {
              "status": "affected",
              "version": "0.0.104",
              "versionType": "semver",
              "lessThanOrEqual": "0.3.6"
            }
          ],
          "packageName": "agents",
          "collectionURL": "https://github.com/cloudflare/agents",
          "defaultStatus": "unaffected"
        }
      ]
    }
  ],
  "published": "2026-02-03T12:16:11.953",
  "references": [
    {
      "url": "https://github.com/cloudflare/agents",
      "source": "cna@cloudflare.com"
    }
  ],
  "vulnStatus": "Deferred",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "cna@cloudflare.com",
      "description": [
        {
          "lang": "en",
          "value": "CWE-639"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "Summary\n\nAn Insecure Direct Object Reference has been found to exist in `createHeaderBasedEmailResolver()` function within the Cloudflare Agents SDK. The issue occurs because the `Message-ID` and `References` headers are parsed to derive the target agentName and agentId without proper validation or origin checks, allowing an external attacker with control of these headers to route inbound mail to arbitrary Durable Object instances and namespaces .\n\n\n\n\nRoot cause\n\nThe `createHeaderBasedEmailResolver()` function lacks cryptographic verification or origin validation for the headers used in the routing logic, effectively allowing external input to dictate internal object routing.\n\n\n\n\nImpact\n\nInsecure Direct Object Reference (IDOR) in email routing lets an attacker steer inbound mail to arbitrary Agent instances via spoofed Message-ID.\n\n\n\n\n\nMitigation:\n\n  *  PR:  https://github.com/cloudflare/agents/blob/main/docs/email.md ] provides the necessary architectural context for coding agents to mitigate the issue by refactoring the resolver to enforce strict identity boundaries.\n  *  Agents-sdk users should  upgrade to agents@0.3.7"
    },
    {
      "lang": "es",
      "value": "Resumen\n\nSe ha encontrado una Referencia Directa Insegura a Objeto que existe en la función 'createHeaderBasedEmailResolver()' dentro del SDK de Cloudflare Agents. El problema ocurre porque los encabezados 'Message-ID' y 'References' se analizan para derivar el agentName y el agentId de destino sin la validación adecuada o comprobaciones de origen, permitiendo a un atacante externo con control de estos encabezados enrutar el correo entrante a instancias y espacios de nombres arbitrarios de Durable Object.\n\nCausa raíz\n\nLa función 'createHeaderBasedEmailResolver()' carece de verificación criptográfica o validación de origen para los encabezados utilizados en la lógica de enrutamiento, permitiendo efectivamente que la entrada externa dicte el enrutamiento interno de objetos.\n\nImpacto\n\nLa Referencia Directa Insegura a Objeto (IDOR) en el enrutamiento de correo electrónico permite a un atacante dirigir el correo entrante a instancias arbitrarias de Agent a través de un Message-ID falsificado.\n\nMitigación:\n\n  * PR: https://github.com/cloudflare/agents/blob/main/docs/email.md ] proporciona el contexto arquitectónico necesario para que los agentes de codificación mitiguen el problema refactorizando el resolvedor para hacer cumplir límites de identidad estrictos.\n  * Los usuarios del SDK de Agents deben actualizar a agents@0.3.7"
    }
  ],
  "lastModified": "2026-06-17T10:16:16.637",
  "sourceIdentifier": "cna@cloudflare.com"
}