USN-3258-1 intended to fix a vulnerability in Dovecot. Further investigation revealed that only Dovecot versions 2.2.26 and newer were affected by the vulnerability. Additionally, the change introduced a regression when Dovecot was configured to use the “dict” authentication database. This update reverts the change. We apologize for the inconvenience.
Original advisory details:
It was discovered that Dovecot incorrectly handled some usernames. An attacker could possibly use this issue to cause Dovecot to hang or crash, resulting in a denial of service.