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.
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-24031.json
https://documentation.open-xchange.com/dovecot/security/advisories/csaf/2026/oxdc-adv-2026-0001.json