CVE-2026-52681Network attack vectorHinoki check available

Mail delivery degradation via reset Sieve accounting

Published Aug 28, 2026 · Updated Aug 28, 2026

Resource-consumption flaw in affected OX Dovecot CE and Pro versions allows remote authenticated users to degrade mail delivery through Sieve. CPU accounting is stored in each compiled script, so repeatedly replacing the active script resets the limit while deleted or renamed scripts leave compiled files behind. Valid account credentials and Sieve access are required; sustained CPU use and accumulating files can slow or interrupt mail delivery.

CVSS severity3.1
Low
EPSS probability0.25%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
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Summary

What happened

Resource-consumption flaw in affected OX Dovecot CE and Pro versions allows remote authenticated users to degrade mail delivery through Sieve. CPU accounting is stored in each compiled script, so repeatedly replacing the active script resets the limit while deleted or renamed scripts leave compiled files behind. Valid account credentials and Sieve access are required; sustained CPU use and accumulating files can slow or interrupt mail delivery.

The record

CVE
CVE-2026-52681
Published
Aug 28, 2026
Updated
Aug 28, 2026
Vendor
Open-Xchange GmbH
Product
OX Dovecot CE
Classifications
CWE-1050, T1499
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=2.3.15 <2.4.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Open-Xchange GmbH · OX Dovecot CEversion=2.3.15 <2.4.5
Open-Xchange GmbH · OX Dovecot Proversion=2.3.15 <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: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-1050Excessive Platform Resource Consumption within a Loop
T1499Endpoint Denial of Service

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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