CVE-2026-27856: Dovecot

Medium severity, CVSS 5.9. EPSS: 0.4% chance of exploitation in the next 30 days.

Doveadm credentials are verified using direct comparison which is susceptible to timing oracle attack. An attacker can use this to determine the configured credentials. Figuring out the credential will lead into full access to the affected component. Limit access to the doveadm http service port, install fixed version. No publicly available exploits are known.

Affected products

• Dovecot Dovecot: before 2.4.3 (fixed in 2.4.3)
• Open-Xchange Dovecot: before 2.3.22.1 (fixed in 2.3.22.1); from 3.0.0, before 3.0.5 (fixed in 3.0.5); from 3.1.0, before 3.1.4 (fixed in 3.1.4)

Published 2026-03-27. Last modified 2026-07-15.