What is CVE-2026-27855?

CVE-2026-27855 is a medium-severity vulnerability in Dovecot, classified under Authentication Bypass by Capture-replay. CVSS score: 6.8/10. Published 2026-03-27.

How severe is CVE-2026-27855?

Medium severity. CVSS v3 base score is 6.8 out of 10.

Vulnerability in Dovecot

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 obser…

EPSS: 0.000 (13.0th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 6.8 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N.

Affected products

Dovecot
Open-xchange Dovecot
Open-xchange Gmbh Ox Dovecot Pro — versions 0

Weakness classification (CWE)

CWE-294 — Authentication Bypass by Capture-replay

References

security@open-xchange.com (vendor-advisory, Vendor Advisory)

Frequently asked questions

What is CVE-2026-27855?: CVE-2026-27855 is a medium-severity vulnerability in Dovecot, classified under Authentication Bypass by Capture-replay. CVSS score: 6.8/10. Published 2026-03-27.
How severe is CVE-2026-27855?: Medium severity. CVSS v3 base score is 6.8 out of 10.