CVE-2026-40874Public exploitNetwork attack vector

Authenticated mail disruption via unchecked forwarding-host deletion

Published Apr 21, 2026 · Updated Apr 21, 2026

Improper access control in mailcow: dockerized before 2026-03b allows remote authenticated users to disrupt mail delivery through its API. The delete branch in data/web/inc/functions.fwdhost.inc.php accepts forwarding-host addresses without applying the administrator-role check used by add and edit actions. Any authenticated account can POST to /api/v1/delete/fwdhost; a configured Forwarding Host must exist, and its removal can interrupt delivery for servers that depend on it.

CVSS severity6.0
Medium
EPSS probability0.17%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Improper access control in mailcow: dockerized before 2026-03b allows remote authenticated users to disrupt mail delivery through its API. The delete branch in data/web/inc/functions.fwdhost.inc.php accepts forwarding-host addresses without applying the administrator-role check used by add and edit actions. Any authenticated account can POST to /api/v1/delete/fwdhost; a configured Forwarding Host must exist, and its removal can interrupt delivery for servers that depend on it.

The record

CVE
CVE-2026-40874
Published
Apr 21, 2026
Updated
Apr 21, 2026
Vendor
mailcow
Product
mailcow: dockerized
Classifications
CWE-284
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 21, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 21, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=< 2026-03b

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

mailcow · mailcow: dockerizedversion=< 2026-03b

Published CVSS scores

6.0mailcow via GitHub Security AdvisoryCVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/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.

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

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-284Improper Access Control

Public exploit references

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

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo