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National Vulnerability Database

National Vulnerability Database

NVD

National Vulnerability Database
  1. Vulnerabilities

CVE-2026-1664 Detail

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 [email protected]


Metrics

 
NVD enrichment efforts reference publicly available information to associate vector strings. CVSS information contributed by other sources is also displayed.
CVSS 4.0 Severity and Vector Strings:

NIST CVSS score
NIST: NVD
N/A
NVD assessment not yet provided.

Nist CVSS score does not match with CNA score
CNA:  Cloudflare, Inc.
CVSS-B 6.9 MEDIUM
Vector:  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

References to Advisories, Solutions, and Tools

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URL Source(s) Tag(s)
https://github.com/cloudflare/agents Cloudflare, Inc.

Weakness Enumeration

CWE-ID CWE Name Source
CWE-639 Authorization Bypass Through User-Controlled Key Cloudflare, Inc.  

Change History

1 change records found show changes

Quick Info

CVE Dictionary Entry:
CVE-2026-1664
NVD Published Date:
02/03/2026
NVD Last Modified:
02/03/2026
Source:
Cloudflare, Inc.