CVE-2026-42395Hinoki check available

Login denial of service via NUL-byte forwarding

Published Aug 28, 2026 · Updated Aug 28, 2026

Denial of service in OX Dovecot CE before 2.4.5 and Pro before 2.3.22.2, 3.0.7, or 3.1.6 allows attackers to crash login processes. The XCLIENT FORWARD parser accepts NUL-bearing forwarding data and carries the malformed value into state consumed by the next login. The source host must be listed as a trusted proxy; successful exploitation terminates the login process and can interrupt subsequent logins.

CVSS severity4.3
Medium
EPSS probability0.18%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Denial of service in OX Dovecot CE before 2.4.5 and Pro before 2.3.22.2, 3.0.7, or 3.1.6 allows attackers to crash login processes. The XCLIENT FORWARD parser accepts NUL-bearing forwarding data and carries the malformed value into state consumed by the next login. The source host must be listed as a trusted proxy; successful exploitation terminates the login process and can interrupt subsequent logins.

The record

CVE
CVE-2026-42395
Published
Aug 28, 2026
Updated
Aug 28, 2026
Vendor
Open-Xchange GmbH
Product
OX Dovecot CE
Classifications
CWE-400, CWE-170, T1499.004
Attack vector
adjacent
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 vectoradjacent
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

6.5Red HatCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
4.3Open-Xchange GmbHCVSS:3.1/AV:A/AC:L/PR:N/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.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
CWE-170Improper Null Termination
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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