Vulnerability-Lookup

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

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

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

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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\", \"supportingMedia\": [{\"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\", \"base64\": false}]}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-639\", \"description\": \"CWE-639 Authorization Bypass Through User-Controlled Key\"}]}], \"providerMetadata\": {\"orgId\": \"a22f1246-ba21-4bb4-a601-ad51614c1513\", \"shortName\": \"cloudflare\", \"dateUpdated\": \"2026-02-03T11:45:10.068Z\"}}}",
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GHSA-R7X9-8PH7-W8CG

Vulnerability from github – Published: 2026-02-03 18:42 – Updated: 2026-02-03 18:42

Summary

Cloudflare Agents SDK has Insecure Direct Object Reference (IDOR) via Header-Based Email Routing

Details

Summary

An Insecure Direct Object Reference (CWE-639) 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.

Patches

Agents-sdk users should upgrade to agents@0.3.7. PR: https://github.com/cloudflare/agents/pull/811 This documentation provides the necessary architectural context for coding agents to mitigate the issue by refactoring the resolver to enforce strict identity boundaries.

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

Show details on source website

JSON

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{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "agents"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.3.7"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-1664"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-639"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-02-03T18:42:01Z",
    "nvd_published_at": "2026-02-03T12:16:11Z",
    "severity": "MODERATE"
  },
  "details": "### Summary\nAn Insecure Direct Object Reference (CWE-639) 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### Root cause\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### Impact\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### Patches\nAgents-sdk users should  upgrade to agents@0.3.7. \nPR: https://github.com/cloudflare/agents/pull/811\nThis [documentation](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.",
  "id": "GHSA-r7x9-8ph7-w8cg",
  "modified": "2026-02-03T18:42:01Z",
  "published": "2026-02-03T18:42:01Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/cloudflare/agents/security/advisories/GHSA-r7x9-8ph7-w8cg"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-1664"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/cloudflare/agents"
    },
    {
      "type": "WEB",
      "url": "https://github.com/cloudflare/agents/blob/main/docs/email.md"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "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",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Cloudflare Agents SDK has Insecure Direct Object Reference (IDOR) via Header-Based Email Routing"
}

FKIE_CVE-2026-1664

Vulnerability from fkie_nvd - Published: 2026-02-03 12:16 - Updated: 2026-02-03 16:44

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

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"
    }
  ],
  "id": "CVE-2026-1664",
  "lastModified": "2026-02-03T16:44:03.343",
  "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": "Awaiting Analysis",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-639"
        }
      ],
      "source": "cna@cloudflare.com",
      "type": "Secondary"
    }
  ]
}

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.

Action not permitted

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

GHSA-R7X9-8PH7-W8CG

Summary

Root cause

Impact

Patches

FKIE_CVE-2026-1664

Tags

Sightings

Nomenclature