# CVE-2026-27855: Dovecot OTP authentication is vulnerable to replay attack under specific conditions. If auth cache is enabled, and…

Source: https://junglewise.ai/threats/cve-2026-27855-dovecot-otp-authentication-is-vulnerable-to-replay-attack-under  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-03-27  
License: CC BY 4.0 with a link back

CVE-2026-27855 · Severity: medium · CVSS 6.8 · Published 2026-03-27

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.

Technologies: [Dovecot](https://junglewise.ai/threats/technologies/dovecot), [Open-Xchange Dovecot](https://junglewise.ai/threats/technologies/open-xchange-dovecot). Vendors: [Dovecot](https://junglewise.ai/threats/vendors/dovecot), [Open-Xchange](https://junglewise.ai/threats/vendors/open-xchange).

## Quick answers

**Is CVE-2026-27855 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-27855 being exploited in the wild.

**How severe is CVE-2026-27855?** Medium severity, with a CVSS score of 6.8, published 27 March 2026.

**Which products and versions are affected?** Dovecot, Open-Xchange Dovecot. The advisory does not name versions.

**Is there a fix for CVE-2026-27855?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**Am I affected by CVE-2026-27855?** Check whether you run Dovecot or Open-Xchange Dovecot. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Affected products

- Dovecot
- Open-Xchange Dovecot

## Related threats

- [Dovecot ManageSieve denial of service via malformed pre-auth command](https://junglewise.ai/threats/cve-2026-33605-dovecot-managesieve-denial-of-service-via-malformed-pre-auth)
- [Open-Xchange Dovecot uncontrolled memory consumption in IMAP](https://junglewise.ai/threats/cve-2026-42006-open-xchange-dovecot-uncontrolled-memory-consumption-in-imap)
- [Open-Xchange Dovecot improper access control in IMAP SETACL](https://junglewise.ai/threats/cve-2026-40020-open-xchange-dovecot-improper-access-control-in-imap-setacl)
- [Open-Xchange Dovecot CPU limit bypass in Sieve scripts](https://junglewise.ai/threats/cve-2026-40016-open-xchange-dovecot-cpu-limit-bypass-in-sieve-scripts)
- [Open-Xchange Dovecot SCRAM TLS channel binding spoofing](https://junglewise.ai/threats/cve-2026-33603-open-xchange-dovecot-scram-tls-channel-binding-spoofing)