CVE-2026-1664
Summary An Insecure Direct Object Reference has been found to exist in `createHeaderBasedEmailResolver()` function within the Cloudflare Agents SDK.
Overview
CVE-2026-1664 is a known-severity vulnerability. It was published on February 3, 2026.
Technical 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
Remediation
Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
References
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Frequently asked questions
What is CVE-2026-1664?
CVE-2026-1664 is a known-severity vulnerability. It was published on February 3, 2026.
How severe is CVE-2026-1664?
CVSS score information is not yet available for this vulnerability. Check back as the CVE record is updated by NVD analysts.
How do I fix or remediate CVE-2026-1664?
Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How can CyberStrike help with CVE-2026-1664?
CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-1664 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.