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
Metrics
Affected Vendors & Products
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| Source | ID | Title |
|---|---|---|
 Github GHSA |
GHSA-r7x9-8ph7-w8cg | Cloudflare Agents SDK has Insecure Direct Object Reference (IDOR) via Header-Based Email Routing |
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
| Link | Providers |
|---|---|
| https://github.com/cloudflare/agents |
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Tue, 03 Feb 2026 15:15:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Metrics |
ssvc
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Tue, 03 Feb 2026 13:15:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | 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 | |
| Title | Insecure Direct Object Reference (IDOR) via Header-Based Email Routing | |
| Weaknesses | CWE-639 | |
| References |
| |
| Metrics |
cvssV4_0
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Projects
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MITRE
Status: PUBLISHED
Assigner: cloudflare
Published:
Updated: 2026-02-03T14:46:36.842Z
Reserved: 2026-01-29T21:09:21.411Z
Link: CVE-2026-1664
Vulnrichment
Updated: 2026-02-03T14:39:52.994Z
NVD
Status : Awaiting Analysis
Published: 2026-02-03T12:16:11.953
Modified: 2026-02-03T16:44:03.343
Link: CVE-2026-1664
Redhat
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OpenCVE Enrichment
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