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GHSA-r7x9-8ph7-w8cg

MediumCVSS 6.9 / 10

Published Feb 3, 2026·Last modified Feb 22, 2026

Affected Components(0)

No affected components available

Description

Summary

An Insecure Direct Object Reference (CWE-639) 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.

Patches

Agents-sdk users should upgrade to agents@0.3.7. PR: https://github.com/cloudflare/agents/pull/811 This documentation provides the necessary architectural context for coding agents to mitigate the issue by refactoring the resolver to enforce strict identity boundaries.

Risk Scores

Base Score

6.9

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability.

Threat Intelligence

2.7

Limited exploitation activity has been observed. Close monitoring and planned remediation are recommended.

EPSS

0.37%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit

Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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Medium severity

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