The cyrus-imapd packages contain a high-performance mail server with IMAP, POP3, NNTP, and Sieve support.
It was discovered that cyrus-imapd did not flush the received commands buffer after switching to TLS encryption for IMAP, LMTP, NNTP, and POP3 sessions. A man-in-the-middle attacker could use this flaw to inject protocol commands into a victim's TLS session initialization messages. This could lead to those commands being processed by cyrus-imapd, potentially allowing the attacker to steal the victim's mail or authentication credentials. (CVE-2011-1926)
Users of cyrus-imapd are advised to upgrade to these updated packages, which contain a backported patch to correct this issue. After installing the update, cyrus-imapd will be restarted automatically.