CyberSecBulletin
CVE-2026-42391NVD status: Deferred

OX Dovecot Pro: Uncontrolled Resource Consumption

Published Updated By the CyberSecBulletin desk

CVE-2026-42391 is a high-severity uncontrolled resource consumption vulnerability in OX Dovecot Pro from Open-Xchange, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions 2.3.22.2, 3.0.7, 3.1.6 as the first without the flaw, so updating OX Dovecot Pro to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.45% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update OX Dovecot Pro to 2.3.22.2 or 3.0.7 or 3.1.6, whichever matches your release line, or a later version.
  2. Update OX Dovecot CE to 2.4.5 or a later version.
  3. Read the advisory on documentation.open-xchange.com for workarounds and exact fixed builds.
  4. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
Open-XchangeOX Dovecot Pro2.3.0 up to, but not including, 2.3.22.2; 3.0.0 up to, but not including, 3.0.7; 3.1.0 up to, but not including, 3.1.62.3.22.2, 3.0.7, 3.1.6
Open-XchangeOX Dovecot CE2.3.0 up to, but not including, 2.4.52.4.5

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
NoneNo data is disclosed.
Integrity
NoneNothing can be modified.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. Scored by CNA (open-xchange.com).

Official description

An unauthenticated attacker can send an IMAP ID command with a very large number of parameters before logging in, which causes memory and CPU usage to grow disproportionately. The login process can be terminated by the out-of-memory handling, which also terminates all other connections handled by the same process. This can cause degradation or denial of service for IMAP logins. Limit the number of connections handled by a single imap-login process. This has a performance impact though. Update to non-vulnerable version. No publicly available exploits are known.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Uncontrolled Resource Consumption

The product does not properly control the allocation and maintenance of a limited resource.

How developers prevent this class of flaw

  • Ensure that protocols have specific limits of scale placed on them.
  • Ensure that all failures in resource allocation place the system into a safe posture.

More Uncontrolled Resource Consumption vulnerabilities (CWE-400)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Other vulnerabilities in OX Dovecot Pro

All OX Dovecot Pro vulnerabilities

Recent Uncontrolled Resource Consumption vulnerabilities

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