Exim is a mail transport agent developed at the University of Cambridge for use on Unix systems connected to the Internet. A buffer overflow flaw was discovered in Exim"s internal string_vformat function. A remote attacker could use this flaw to execute arbitrary code on the mail server running Exim. Note: successful exploitation would allow a remote attacker to execute arbitrary code as root on a Red Hat Enterprise Linux 4 or 5 system that is running the Exim mail server. An exploit for this issue is known to exist. For additional information regarding this flaw, along with mitigation advice, please see the Knowledge Base article linked to in the References section of this advisory. Users of Exim are advised to update to these erratum packages which contain a backported patch to correct this issue. After installing this update, the Exim daemon will be restarted automatically.