Cyrus 2.0.15, 2.0.16, and 1.6.24 on BSDi 4.2, with IMAP enabled, allows remote attackers to cause a denial of service (hang) using PHP IMAP clients.
https://exchange.xforce.ibmcloud.com/vulnerabilities/7053
https://euvd.enisa.europa.eu/vulnerability/EUVD-2001-1135