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CVE-2026-1664— Insecure Direct Object Reference (IDOR) via Header-Based Email Routing

Quick assessment

Affected
CVE-2026-1664
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Cloudflare Agents是Cloudflare开源的一个在Cloudflare上构建和部署AI代理的工具。 Cloudflare Agents存在安全漏洞，该漏洞源于createHeaderBasedEmailResolver函数解析Message-ID和References标头时缺乏验证，可能导致不安全的直接对象引用攻击，使攻击者可将入站邮件路由至任意Durable Object实例和命名空间。

AI Predicted 8.6 Difficulty: Easy EPSS 0.47% · P39

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

I. Basic Information for CVE-2026-1664

Vulnerability Information
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Vulnerability Title
Insecure Direct Object Reference (IDOR) via Header-Based Email Routing
Source: CVE Program / CVE List V5
Vulnerability 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
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
通过用户控制密钥绕过授权机制
Source: CVE Program / CVE List V5
Vulnerability Title
Cloudflare Agents 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Cloudflare Agents是Cloudflare开源的一个在Cloudflare上构建和部署AI代理的工具。 Cloudflare Agents存在安全漏洞，该漏洞源于createHeaderBasedEmailResolver函数解析Message-ID和References标头时缺乏验证，可能导致不安全的直接对象引用攻击，使攻击者可将入站邮件路由至任意Durable Object实例和命名空间。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

II. Public POCs for CVE-2026-1664

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III. Intelligence Information for CVE-2026-1664

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IV. Related Vulnerabilities

Same weakness: CWE-639

V. Comments for CVE-2026-1664

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