VulnerabilityAnalyzed

CVE-2026-27855

Dovecot OTP authentication is vulnerable to replay attack under specific conditions.

MEDIUM 5.9EPSS 0.31%

Does this matter?

Lower severity and a low EPSS score (0.31%). Track it; it rarely justifies an emergency change on its own.

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.

CVSS 3.1: 5.9 MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
EPSS: 0.31% probability · 24th percentile
CISA KEV: Not listed
Weakness: CWE-294
Affected: dovecot/dovecot · open-xchange/dovecot
Source: security@open-xchange.com

References

https://documentation.open-xchange.com/dovecot/security/advisories/csaf/2026/oxdc-adv-2026-0001.jsonVendor Advisory

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.