CVE-2026-27855

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.

PUBLISHED Reserved 2026-02-24 | Published 2026-03-27 | Updated 2026-03-27 | Assigner OX

Problem types

Authentication Bypass by Capture-replay

Product status

References

documentation.open-xchange.com/...26/oxdc-adv-2026-0001.json vendor-advisory

cve.org (CVE-2026-27855)

nvd.nist.gov (CVE-2026-27855)

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