Ubuntu Security Notice 387-1 – Dovecot was discovered to have an error when handling its index cache files. This error could be exploited by authenticated POP and IMAP users to cause a crash of the Dovecot server, or possibly to execute arbitrary code. Only servers using the non-default option “mmap_disable=yes” were vulnerable.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/52621/USN-387-1.txt
Source: https://packetstormsecurity.com/files/52621/Ubuntu-Security-Notice-387-1.html