(RHSA-2011:0859) Moderate: cyrus-imapd security update

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.