CVE-2026-33604Network attack vector

Spoofed email injection via incomplete dot-stuffing

Published Aug 28, 2026 · Updated Aug 28, 2026

SMTP smuggling in OX Dovecot CE and Pro allows remote attackers to inject spoofed email through outbound message relaying. The core SMTP outbound dot-stuffing path fails to escape a dot following a bare carriage return, letting a downstream server treat an injected end-of-data sequence as new SMTP commands. Exploitation requires Dovecot to relay the crafted message and a receiving server that still accepts bare carriage returns.

CVSS severity5.9
Medium
EPSS probability0.27%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

SMTP smuggling in OX Dovecot CE and Pro allows remote attackers to inject spoofed email through outbound message relaying. The core SMTP outbound dot-stuffing path fails to escape a dot following a bare carriage return, letting a downstream server treat an injected end-of-data sequence as new SMTP commands. Exploitation requires Dovecot to relay the crafted message and a receiving server that still accepts bare carriage returns.

The record

CVE
CVE-2026-33604
Published
Aug 28, 2026
Updated
Aug 28, 2026
Vendor
Open-Xchange GmbH
Product
OX Dovecot CE
Classifications
CWE-655
Attack vector
network
Privileges
unauthenticated

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 privilegesunauthenticated

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

5.9Open-Xchange GmbHCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/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 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-655Insufficient Psychological Acceptability

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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