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
CVSS
No CVSS.
References
| Link | Resource |
|---|---|
| https://github.com/cloudflare/agents |
Configurations
No configuration.
History
No history.
Information
Published : 2026-02-03 12:16
Updated : 2026-02-03 16:44
NVD link : CVE-2026-1664
Mitre link : CVE-2026-1664
CVE.ORG link : CVE-2026-1664
JSON object : View
Products Affected
No product.
CWE
CWE-639
Authorization Bypass Through User-Controlled Key