GEN:SID 1:2596
Message SMTP BCC command overflow attempt
Summary This event is generated when an attempt is made to exploit a buffer overflow
associated with the Mail Transfer Agent Exim.
Impact A successful attack may allow the execution of arbitrary code on a vulnerable
server with the privilege of the process running Exim.
Detailed Information Exim is vulnerable to a buffer overflow, permitting an attacker to execute
arbitrary code.  The vulnerability may be exploited if Exim is configured to
verify header syntax in the e-mail message body.  This is not the default
configuration.  If an attacker supplies a large number of spaces after certain
header fields, it may be possible to cause a buffer overflow.
Affected Systems Exim prior to version 4.34
Attack Scenarios An attacker can create and send mail with a malformed header,
possibly causing a buffer overflow and permitting the execution of arbitrary code.
Ease of Attack Simple.
Corrective Action Upgrade to the latest non-affected version of the software.
Additional References  
Rule References bugtraq: 10291
cve: 2004-0400
url: www.guninski.com/exim1.html