CVE-2026-1664Network attack vector

Unauthenticated email rerouting via spoofed routing headers

Published Feb 3, 2026 · Updated Feb 3, 2026

IDOR in Cloudflare Agents before 0.3.7 allows remote attackers to route inbound email to arbitrary Agent instances via forged headers. createHeaderBasedEmailResolver() trusts Message-ID and References values to derive agentName and agentId without origin or cryptographic validation. Exploitation requires an application to use this resolver for inbound email; successful routing crosses Agent namespace and instance boundaries.

CVSS severity6.9
Medium
EPSS probability0.38%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

IDOR in Cloudflare Agents before 0.3.7 allows remote attackers to route inbound email to arbitrary Agent instances via forged headers. createHeaderBasedEmailResolver() trusts Message-ID and References values to derive agentName and agentId without origin or cryptographic validation. Exploitation requires an application to use this resolver for inbound email; successful routing crosses Agent namespace and instance boundaries.

The record

CVE
CVE-2026-1664
Published
Feb 3, 2026
Updated
Feb 3, 2026
Vendor
Cloudflare
Product
Cloudflare Agents
Classifications
CWE-639, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 3, 2026CVE publishedPublication date reported by the CVE source.
  2. Feb 3, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0.0.104 <=0.3.6

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Cloudflare · Cloudflare Agentsversion=0.0.104 <=0.3.6

Published CVSS scores

6.9Cloudflare, Inc.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

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-639Authorization Bypass Through User-Controlled Key
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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