CVE-2026-27860: Dovecot

Medium severity, CVSS 5.3. EPSS: 0.3% chance of exploitation in the next 30 days.

If auth_username_chars is empty, it is possible to inject arbitrary LDAP filter to Dovecot's LDAP authentication. This leads to potentially bypassing restrictions and allows probing of LDAP structure. Do not clear out auth_username_chars, or 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 3.1.4 (fixed in 3.1.4)

Published 2026-03-27. Last modified 2026-06-17.