CVE-2026-33603: Dovecot

Medium severity, CVSS 5.3. EPSS: 0.2% chance of exploitation in the next 30 days.

Attacker can use a specially crafted base64 exchange between Dovecot and Client to fake SCRAM TLS channel binding. This requires that the attacker is able to position itself between Dovecot and the client connection. If successful, the attacker can eavesdrop communications between Dovecot and client as MITM proxy. Install fixed version. No publicly available exploits are known.

Affected products

• Dovecot Dovecot: before 2.4.4 (fixed in 2.4.4)
• Open-Xchange Dovecot: before 3.1.5 (fixed in 3.1.5)

Published 2026-05-12. Last modified 2026-06-17.