Vulnerability-Lookup

FKIE_CVE-2026-1664

Vulnerability from fkie_nvd - Published: 2026-02-03 12:16 - Updated: 2026-04-15 00:35

Severity ?

6.9 (Medium) - 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

Summary

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

References

	URL	Tags
	cna@cloudflare.com	https://github.com/cloudflare/agents

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "cveTags": [],
  "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 funci\u00f3n \u0027createHeaderBasedEmailResolver()\u0027 dentro del SDK de Cloudflare Agents. El problema ocurre porque los encabezados \u0027Message-ID\u0027 y \u0027References\u0027 se analizan para derivar el agentName y el agentId de destino sin la validaci\u00f3n 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 ra\u00edz\n\nLa funci\u00f3n \u0027createHeaderBasedEmailResolver()\u0027 carece de verificaci\u00f3n criptogr\u00e1fica o validaci\u00f3n de origen para los encabezados utilizados en la l\u00f3gica 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 electr\u00f3nico permite a un atacante dirigir el correo entrante a instancias arbitrarias de Agent a trav\u00e9s de un Message-ID falsificado.\n\nMitigaci\u00f3n:\n\n  * PR: https://github.com/cloudflare/agents/blob/main/docs/email.md ] proporciona el contexto arquitect\u00f3nico necesario para que los agentes de codificaci\u00f3n mitiguen el problema refactorizando el resolvedor para hacer cumplir l\u00edmites de identidad estrictos.\n  * Los usuarios del SDK de Agents deben actualizar a agents@0.3.7"
    }
  ],
  "id": "CVE-2026-1664",
  "lastModified": "2026-04-15T00:35:42.020",
  "metrics": {
    "cvssMetricV40": [
      {
        "cvssData": {
          "Automatable": "NOT_DEFINED",
          "Recovery": "NOT_DEFINED",
          "Safety": "NOT_DEFINED",
          "attackComplexity": "LOW",
          "attackRequirements": "NONE",
          "attackVector": "NETWORK",
          "availabilityRequirement": "NOT_DEFINED",
          "baseScore": 6.9,
          "baseSeverity": "MEDIUM",
          "confidentialityRequirement": "NOT_DEFINED",
          "exploitMaturity": "NOT_DEFINED",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "privilegesRequired": "NONE",
          "providerUrgency": "NOT_DEFINED",
          "subAvailabilityImpact": "NONE",
          "subConfidentialityImpact": "LOW",
          "subIntegrityImpact": "LOW",
          "userInteraction": "NONE",
          "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",
          "version": "4.0",
          "vulnAvailabilityImpact": "NONE",
          "vulnConfidentialityImpact": "LOW",
          "vulnIntegrityImpact": "LOW",
          "vulnerabilityResponseEffort": "NOT_DEFINED"
        },
        "source": "cna@cloudflare.com",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-02-03T12:16:11.953",
  "references": [
    {
      "source": "cna@cloudflare.com",
      "url": "https://github.com/cloudflare/agents"
    }
  ],
  "sourceIdentifier": "cna@cloudflare.com",
  "vulnStatus": "Deferred",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-639"
        }
      ],
      "source": "cna@cloudflare.com",
      "type": "Secondary"
    }
  ]
}

CVE-2026-1664 (GCVE-0-2026-1664)

Vulnerability from cvelistv5 – Published: 2026-02-03 11:39 – Updated: 2026-02-03 14:46

Title

Insecure Direct Object Reference (IDOR) via Header-Based Email Routing

Summary

Severity ?

6.9 (Medium)


                        
                          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

CWE

CWE-639 - Authorization Bypass Through User-Controlled Key

Assigner

cloudflare

References

URL

Tags

https://github.com/cloudflare/agents

Impacted products

	Vendor	Product	Version
			Affected: 0.0.104 , ≤ 0.3.6 (semver)

Credits

asukalangley

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-1664",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-02-03T14:38:24.747542Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-02-03T14:46:36.842Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "collectionURL": "https://github.com/cloudflare/agents",
          "defaultStatus": "unaffected",
          "packageName": "agents",
          "repo": "https://github.com/cloudflare/agents",
          "versions": [
            {
              "lessThanOrEqual": "0.3.6",
              "status": "affected",
              "version": "0.0.104",
              "versionType": "semver"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "reporter",
          "value": "asukalangley"
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "supportingMedia": [
            {
              "base64": false,
              "type": "text/html",
              "value": "\u003cb\u003e\u003cp\u003e\u003cspan style=\"background-color: transparent;\"\u003eSummary\u003c/span\u003e\u003c/p\u003e\u003c/b\u003e\u003cp\u003eAn 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 .\u003c/p\u003e\u003cb\u003e\u003cp\u003e\u003cspan style=\"background-color: transparent;\"\u003e\u003cbr\u003e\u003c/span\u003e\u003c/p\u003e\u003cp\u003e\u003cspan style=\"background-color: transparent;\"\u003eRoot cause\u003c/span\u003e\u003c/p\u003e\u003c/b\u003e\u003cp\u003e\u003cspan style=\"background-color: transparent;\"\u003eThe `\u003c/span\u003e\u003cspan style=\"background-color: transparent;\"\u003ecreateHeaderBasedEmailResolver()`\u003c/span\u003e\u003cspan style=\"background-color: transparent;\"\u003e function lacks cryptographic verification or origin validation for the headers used in the routing logic, effectively allowing external input to dictate internal object routing.\u003c/span\u003e\u003c/p\u003e\u003cb\u003e\u003cp\u003e\u003cspan style=\"background-color: transparent;\"\u003e\u003cbr\u003e\u003c/span\u003e\u003c/p\u003e\u003cp\u003e\u003cspan style=\"background-color: transparent;\"\u003eImpact\u003c/span\u003e\u003c/p\u003e\u003c/b\u003e\u003cp\u003e\u003cspan style=\"background-color: transparent;\"\u003eInsecure Direct Object Reference (IDOR) in email routing lets an attacker steer inbound mail to arbitrary Agent instances via spoofed Message-ID.\u003c/span\u003e\u003cbr\u003e\u003c/p\u003e\u003cp\u003e\u003cspan style=\"background-color: transparent;\"\u003e\u003cbr\u003e\u003c/span\u003e\u003c/p\u003e\u003cp\u003e\u003cspan style=\"background-color: transparent;\"\u003e\u003cb\u003eMitigation:\u003c/b\u003e\u003c/span\u003e\u003c/p\u003e\u003cul\u003e\u003cli\u003e\u003cspan style=\"background-color: transparent;\"\u003ePR: \u003c/span\u003e\u003ca target=\"_blank\" rel=\"nofollow\" href=\"https://github.com/cloudflare/agents/pull/811\"\u003e\u003cspan style=\"background-color: transparent;\"\u003ehttps://github.com/cloudflare/agents/pull/811\u003c/span\u003e\u003c/a\u003e\u003c/li\u003e\u003cli\u003eThis \u003ca target=\"_blank\" rel=\"nofollow\" href=\"https://github.com/cloudflare/agents/blob/main/docs/email.md\"\u003e\u003cspan style=\"background-color: transparent;\"\u003edocumentation\u003c/span\u003e\u003c/a\u003e\u003cspan style=\"background-color: transparent;\"\u003e\u0026nbsp;[\u003ca target=\"_blank\" rel=\"nofollow\" href=\"https://github.com/cloudflare/agents/blob/main/docs/email.md\"\u003ehttps://github.com/cloudflare/agents/blob/main/docs/email.md\u003c/a\u003e] provides the necessary architectural context for coding agents to mitigate the issue by refactoring the resolver to enforce strict identity boundaries.\u003c/span\u003e\u003c/li\u003e\u003cli\u003eAgents-sdk users should  upgrade to \u003cspan style=\"background-color: transparent;\"\u003eagents@0.3.7\u003c/span\u003e\u003c/li\u003e\u003c/ul\u003e\u003cp\u003e\u003c/p\u003e\u003cb\u003e\u003c/b\u003e"
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            "Recovery": "NOT_DEFINED",
            "Safety": "NOT_DEFINED",
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "baseScore": 6.9,
            "baseSeverity": "MEDIUM",
            "exploitMaturity": "NOT_DEFINED",
            "privilegesRequired": "NONE",
            "providerUrgency": "NOT_DEFINED",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "LOW",
            "subIntegrityImpact": "LOW",
            "userInteraction": "NONE",
            "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",
            "version": "4.0",
            "vulnAvailabilityImpact": "NONE",
            "vulnConfidentialityImpact": "LOW",
            "vulnIntegrityImpact": "LOW",
            "vulnerabilityResponseEffort": "NOT_DEFINED"
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          "scenarios": [
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              "lang": "en",
              "value": "GENERAL"
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      "problemTypes": [
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          "descriptions": [
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              "description": "CWE-639 Authorization Bypass Through User-Controlled Key",
              "lang": "en",
              "type": "CWE"
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        "orgId": "a22f1246-ba21-4bb4-a601-ad51614c1513",
        "shortName": "cloudflare"
      },
      "references": [
        {
          "url": "https://github.com/cloudflare/agents"
        }
      ],
      "source": {
        "discovery": "UNKNOWN"
      },
      "title": "Insecure Direct Object Reference (IDOR) via Header-Based Email Routing",
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        "engine": "Vulnogram 0.5.0"
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  "cveMetadata": {
    "assignerOrgId": "a22f1246-ba21-4bb4-a601-ad51614c1513",
    "assignerShortName": "cloudflare",
    "cveId": "CVE-2026-1664",
    "datePublished": "2026-02-03T11:39:18.810Z",
    "dateReserved": "2026-01-29T21:09:21.411Z",
    "dateUpdated": "2026-02-03T14:46:36.842Z",
    "state": "PUBLISHED"
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  "dataType": "CVE_RECORD",
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}

Sightings

Author	Source	Type	Date

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

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FKIE_CVE-2026-1664

CVE-2026-1664 (GCVE-0-2026-1664)

Tags

Sightings

Nomenclature