CVE-2026-27855

| EUVD-2026-16563 MEDIUM
2026-03-27 OX GHSA-7923-h3mf-4442
6.8
CVSS 3.1
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CVSS Vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

Lifecycle Timeline

4
Patch Released
Mar 31, 2026 - 13:49 nvd
Patch available
EUVD ID Assigned
Mar 27, 2026 - 08:30 euvd
EUVD-2026-16563
Analysis Generated
Mar 27, 2026 - 08:30 vuln.today
CVE Published
Mar 27, 2026 - 08:10 nvd
MEDIUM 6.8

Tags

Microsoft Information Disclosure Redhat

Description

Dovecot OTP authentication is vulnerable to replay attack under specific conditions. If auth cache is enabled, and username is altered in passdb, then OTP credentials can be cached so that same OTP reply is valid. An attacker able to observe an OTP exchange is able to log in as the user. If authentication happens over unsecure connection, switch to SCRAM protocol. Alternatively ensure the communcations are secured, and if possible switch to OAUTH2 or SCRAM. No publicly available exploits are known.

Analysis

Dovecot OTP authentication enables replay attacks when authentication cache is enabled and username alteration occurs in passdb, allowing attackers who observe an OTP exchange to authenticate as the targeted user. Open-XChange Dovecot Pro is affected (CPE: cpe:2.3:a:open-xchange_gmbh:ox_dovecot_pro:*:*:*:*:*:*:*:*). …

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Remediation

Within 30 days: Identify affected systems and apply vendor patches as part of regular patch cycle. Monitor vendor channels for patch availability.

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Priority Score

34
Low Medium High Critical
KEV: 0
EPSS: +0.0
CVSS: +34
POC: 0

Vendor Status

Ubuntu

Priority: Medium
dovecot
Release Status Version
trusty needed -
xenial needed -
bionic needed -
focal needed -
jammy needed -
noble needed -
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) -

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CVE-2026-27855 vulnerability details – vuln.today
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