CVE-2026-40204Network attack vector

Authenticated mailbox ACL bypass via lda_mailbox_autocreate

Published Aug 28, 2026 · Updated Aug 28, 2026

Improper access control in affected OX Dovecot CE and Pro releases allows remote authenticated users to bypass mailbox ACL restrictions. The vendor identifies the locus as ACL handling for lda_mailbox_autocreate but has not disclosed the exact erroneous operation. Exploitation requires valid low-privileged credentials and high-complexity network interaction; no further impact has been published.

CVSS severity3.1
Low
EPSS probability0.18%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper access control in affected OX Dovecot CE and Pro releases allows remote authenticated users to bypass mailbox ACL restrictions. The vendor identifies the locus as ACL handling for lda_mailbox_autocreate but has not disclosed the exact erroneous operation. Exploitation requires valid low-privileged credentials and high-complexity network interaction; no further impact has been published.

The record

CVE
CVE-2026-40204
Published
Aug 28, 2026
Updated
Aug 28, 2026
Vendor
Open-Xchange GmbH
Product
OX Dovecot CE
Classifications
CWE-284
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 28, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 28, 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=2.3.0 <2.4.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Open-Xchange GmbH · OX Dovecot CEversion=2.3.0 <2.4.5
Open-Xchange GmbH · OX Dovecot Proversion=2.3.0 <2.3.22.2; version=3.0.0 <3.0.7; version=3.1.0 <3.1.6

Published CVSS scores

3.1Open-Xchange GmbHCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A: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 exploitUnconfirmed

Weakness, pattern, technique

CWE-284Improper Access Control

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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