Sendmail is a very widely used Mail Transport Agent (MTA). MTAs delivermail from one machine to another. Sendmail is not a client program, butrather a behind-the-scenes daemon that moves email over networks or theInternet to its final destination.The configuration of sendmail in Red Hat Enterprise Linux was found to notreject the "localhost.localdomain" domain name for email messages that comefrom external hosts. This could allow remote attackers to disguise spoofedmessages. (CVE-2006-7176)A flaw was found in the way sendmail handled NUL characters in theCommonName field of X.509 certificates. An attacker able to get acarefully-crafted certificate signed by a trusted Certificate Authoritycould trick sendmail into accepting it by mistake, allowing the attacker toperform a man-in-the-middle attack or bypass intended client certificateauthentication. (CVE-2009-4565)Note: The CVE-2009-4565 issue only affected configurations using TLS withcertificate verification and CommonName checking enabled, which is not atypical configuration.This update also fixes the following bugs:All users of sendmail are advised to upgrade to these updated packages,which resolve these issues.