The ClamAV Mail fILTER (clamav-milter) 0.84 through 0.85d, when used in Sendmail using long timeouts, allows remote attackers to cause a denial of service by keeping an open connection, which prevents ClamAV from reloading.
http://www.securityfocus.com/bid/14047
http://www.novell.com/linux/security/advisories/2005_38_clamav.html