Fetchmail is a remote mail retrieval and forwarding utility intended for use over on-demand TCP/IP links, such as SLIP and PPP connections. It was discovered that fetchmail is affected by the previously published "null prefix attack", caused by incorrect handling of NULL characters in X.509 certificates. If an attacker is able to get a carefully-crafted certificate signed by a trusted Certificate Authority, the attacker could use the certificate during a man-in-the-middle attack and potentially confuse fetchmail into accepting it by mistake. A flaw was found in the way fetchmail handles rejections from a remote SMTP server when sending warning mail to the postmaster. If fetchmail sent a warning mail to the postmaster of an SMTP server and that SMTP server rejected it, fetchmail could crash. A flaw was found in fetchmail. When fetchmail is run in double verbose mode , it could crash upon receiving certain, malformed mail messages with long headers. A remote attacker could use this flaw to cause a denial of service if fetchmail was also running in daemon mode . Note: when using SSL-enabled services, it is recommended that the fetchmail "--sslcertck" option be used to enforce strict SSL certificate checking. All fetchmail users should upgrade to this updated package, which contains backported patches to correct these issues. If fetchmail is running in daemon mode, it must be restarted for this update to take effect .