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Ox Dovecot Pro CVE-2025-59028

| EUVDEUVD-2025-209088 MEDIUM
Improper Input Validation (CWE-20)
2026-03-27 OX GHSA-9q9x-wwfr-fxqm
Information Disclosure Ox Dovecot Pro
5.3
CVSS 3.1 · NVD
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Severity by source

NVD PRIMARY
5.3 MEDIUM
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Ubuntu
MEDIUM
qualitative
SUSE
MEDIUM
qualitative
Red Hat
5.3 MEDIUM
qualitative

Primary rating from NVD.

CVSS VectorNVD

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
Low

Lifecycle Timeline

4
Patch released
Mar 31, 2026 - 13:49 nvd
Patch available
EUVD ID Assigned
Mar 27, 2026 - 08:30 euvd
EUVD-2025-209088
Analysis Generated
Mar 27, 2026 - 08:30 vuln.today
CVE Published
Mar 27, 2026 - 08:10 nvd
MEDIUM 5.3

DescriptionCVE.org

When sending invalid base64 SASL data, login process is disconnected from the auth server, causing all active authentication sessions to fail. Invalid BASE64 data can be used to DoS a vulnerable server to break concurrent logins. Install fixed version or disable concurrency in login processes (heavy perfomance penalty on large deployments). No publicly available exploits are known.

AnalysisAI

OX Dovecot Pro authentication server becomes disconnected when processing invalid base64 SASL data, causing all concurrent active authentication sessions to fail and enabling denial-of-service attacks against login infrastructure. Unauthenticated remote attackers can trigger this condition with minimal attack complexity by sending malformed base64 sequences to the SASL authentication handler. No public exploit code is currently available, and the vulnerability carries a CVSS score of 5.3 reflecting limited availability impact without confidentiality or integrity compromise.

Technical ContextAI

The vulnerability resides in the SASL (Simple Authentication and Security Layer) authentication mechanism implemented within OX Dovecot Pro (CPE:cpe:2.3:a:open-xchange_gmbh:ox_dovecot_pro:*:*:*:*:*:*:*:*). The root cause is classified under CWE-20 (Improper Input Validation), indicating insufficient validation of base64-encoded authentication data before processing. When the SASL handler receives malformed or invalid base64 sequences, the authentication server unexpectedly disconnects from its authentication subsystem rather than gracefully rejecting the malformed input. This architectural failure cascades to terminate all concurrent authentication sessions sharing the same server instance, as the entire authentication channel is severed rather than isolated to the offending request. The vulnerability exposes a gap in input sanitization and error handling within the base64 decoding and SASL protocol state machine.

RemediationAI

Upgrade OX Dovecot Pro to the patched version specified in the vendor advisory at https://documentation.open-xchange.com/dovecot/security/advisories/csaf/2026/oxdc-adv-2026-0001.json. The vendor advisory notes that a fixed version is available, though the specific version number requires consultation of the CSAF document. As an interim mitigation prior to patch deployment, the vendor recommends disabling concurrency in login processes, though this introduces a significant performance penalty on large deployments and should be considered a temporary measure only. Organizations should also implement network-level rate limiting on SASL authentication endpoints to reduce the effective denial-of-service surface, and consider isolating Dovecot Pro instances with connection-state monitoring to rapidly detect and contain cascading session failures.

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Same weakness CWE-20 – Improper Input Validation

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CVE-2009-0927 HIGH POC
8.8
CVE-2017-9791 CRITICAL POC
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CVE-2017-15944 CRITICAL POC
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CVE-2019-0604 CRITICAL POC
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Same technique Information Disclosure

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CVE-2019-2725 CRITICAL POC
9.8
CVE-2021-34523 CRITICAL POC
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CVE-2013-2251 CRITICAL POC
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CVE-2017-5638 CRITICAL POC
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CVE-2025-24813 CRITICAL POC
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CVE-2015-1701 HIGH POC
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CVE-2017-0147 HIGH POC
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CVE-2014-6324 HIGH POC
8.8

Vendor StatusVendor

Ubuntu

Priority: Medium
dovecot
Release Status Version
trusty not-affected 2.4.1+ only
xenial not-affected 2.4.1+ only
bionic not-affected 2.4.1+ only
focal not-affected 2.4.1+ only
jammy not-affected 2.4.1+ only
noble not-affected 2.4.1+ only
questing needed -
upstream released 2.4.3

Debian

dovecot
Release Status Fixed Version Urgency
bullseye vulnerable 1:2.3.13+dfsg1-2+deb11u1 -
bullseye (security) vulnerable 1:2.3.13+dfsg1-2+deb11u2 -
bookworm, bookworm (security) vulnerable 1:2.3.19.1+dfsg1-2.1+deb12u1 -
trixie vulnerable 1:2.4.1+dfsg1-6+deb13u3 -
trixie (security) vulnerable 1:2.4.1+dfsg1-6+deb13u1 -
forky, sid vulnerable 1:2.4.2+dfsg1-4 -
(unstable) fixed (unfixed) -

SUSE

Severity: Medium
Product Status
SUSE Linux Enterprise High Performance Computing 15 SP7 Fixed
SUSE Linux Enterprise High Performance Computing 15 SP7 Fixed
SUSE Linux Enterprise Module for Server Applications 15 SP7 Fixed
SUSE Linux Enterprise Module for Server Applications 15 SP7 Fixed
SUSE Linux Enterprise Server 15 SP7 Fixed

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CVE-2025-59028 vulnerability details – vuln.today
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