Dovecot SQL based authentication can be bypassed when auth_username_chars is cleared by admin. This vulnerability allows bypassing authentication for any user and user enumeration. Do not clear auth_username_chars. If this is not possible, install latest fixed version. No publicly available exploits are known.
Exploitability
AV:NAC:HPR:NUI:NScope
S:UImpact
C:HI:HA:L7.7/CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:LInjection