CVE-2026-73209Network attack vectorHinoki check available

Authenticated IMAP crash via recursive decompression

Published Aug 28, 2026 · Updated Aug 28, 2026

Uncontrolled recursion in Open-Xchange OX Dovecot CE and Pro allows remote authenticated users to crash IMAP via compressed data. The imap-login decompression path recursively processes zero-output chunks instead of unwinding, exhausting the process stack. Valid IMAP credentials and enabled session compression are required; termination of the login process degrades or denies IMAP access.

CVSS severity6.5
Medium
EPSS probability0.32%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Uncontrolled recursion in Open-Xchange OX Dovecot CE and Pro allows remote authenticated users to crash IMAP via compressed data. The imap-login decompression path recursively processes zero-output chunks instead of unwinding, exhausting the process stack. Valid IMAP credentials and enabled session compression are required; termination of the login process degrades or denies IMAP access.

The record

CVE
CVE-2026-73209
Published
Aug 28, 2026
Updated
Aug 28, 2026
Vendor
Open-Xchange GmbH
Product
OX Dovecot CE
Classifications
CWE-674, 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 <2.3.22.2; version=3.0.0 <3.0.7; version=3.1.0 <3.1.6

Published CVSS scores

6.5Open-Xchange GmbHCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

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.

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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-674Uncontrolled Recursion
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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