CVE-2026-33607Network attack vector

Authenticated IMAP denial of service via exponential backtracking

Published Aug 28, 2026 · Updated Aug 28, 2026

Uncontrolled resource consumption in affected OX Dovecot CE and Pro versions allows remote authenticated users to interrupt IMAP service. The core IMAP LIST match_sub() routine applies exponential-backtracking matching to attacker-controlled input, driving CPU consumption. A valid mailbox account and network access to IMAP are required; repeated commands degrade or deny IMAP availability without affecting confidentiality or integrity.

CVSS severity4.3
Medium
EPSS probability0.29%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Uncontrolled resource consumption in affected OX Dovecot CE and Pro versions allows remote authenticated users to interrupt IMAP service. The core IMAP LIST match_sub() routine applies exponential-backtracking matching to attacker-controlled input, driving CPU consumption. A valid mailbox account and network access to IMAP are required; repeated commands degrade or deny IMAP availability without affecting confidentiality or integrity.

The record

CVE
CVE-2026-33607
Published
Aug 28, 2026
Updated
Aug 28, 2026
Vendor
Open-Xchange GmbH
Product
OX Dovecot CE
Classifications
CWE-400, T1499.004
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 <3.0.7; version=3.1.0 <3.1.6

Published CVSS scores

4.3Open-Xchange GmbHCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L

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-400Uncontrolled Resource Consumption
T1499.004Application or System Exploitation

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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