CVE-2026-27855

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.

Affected products

Dovecot, Linuxmint, Red Os, Ubuntu

Dovecot

< 2.4.3

Open-xchange Dovecot

≤ 2.3.0

Fix

Available

CVSS 3.1

6.8 MEDIUM

EPSS

0.3% (24th percentile)

Weakness

CWE-294

NVD status

Analyzed

Published

2026-03-27