CVE-2026-86009Public exploitNetwork attack vectorHinoki check available

Cross-domain spoofing via unscoped sender authorization

Published Oct 16, 2026 · Updated Oct 16, 2026

Authorization bypass in Mailu allows remote authenticated users to spoof other hosted domains through sender-login lookups. The postfix_sender_login function includes every account with allow_spoofing enabled without restricting the lookup to the requested sender's domain. Domain-manager access permits enabling that flag, allowing impersonation of another hosted domain with DKIM/SPF-authenticated email.

CVSS severityUnavailable
Unscored
EPSS probability0.30%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Authorization bypass in Mailu allows remote authenticated users to spoof other hosted domains through sender-login lookups. The postfix_sender_login function includes every account with allow_spoofing enabled without restricting the lookup to the requested sender's domain. Domain-manager access permits enabling that flag, allowing impersonation of another hosted domain with DKIM/SPF-authenticated email.

The record

CVE
CVE-2026-86009
Published
Oct 16, 2026
Updated
Oct 16, 2026
Vendor
Mailu
Product
Mailu
Classifications
CWE-285
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Oct 16, 2026CVE publishedPublication date reported by the CVE source.
  2. Oct 16, 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=< f05aeb8322e2f61096af6b089d61ba6f40587d96

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Mailu · Mailuversion=< f05aeb8322e2f61096af6b089d61ba6f40587d96

Published CVSS scores

No CVSS assessment is available in this record.

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.

Activity data is delayed. The latest report is Sep 28, 2026.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-285Improper Authorization

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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