A security issue affects these releases of Ubuntu and its derivatives:
- Ubuntu 16.10
- Ubuntu 16.04 LTS
USN-3258-1 introduced a regression in Dovecot.
- dovecot: IMAP and POP3 email server
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.
The problem can be corrected by updating your system to the following