CVE-2026-1664 (GCVE-0-2026-1664)
Vulnerability from cvelistv5 – Published: 2026-02-03 11:39 – Updated: 2026-02-03 14:46
VLAI
EPSS
VEX
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
SSVC
Exploitation: none
Automatable: yes
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-02-03 14:38 UTC
CWE
- CWE-639 - Authorization Bypass Through User-Controlled Key
Assigner
cloudflare
CNA
References
1 reference
| URL | Tags |
|---|---|
| https://github.com/cloudflare/agents |
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