This script is Copyright (C) 2016-2017 Tenable Network Security, Inc.
The remote FreeBSD host is missing a security-related update.
The Exim project reports :
Exim leaks the private DKIM signing key to the log files.
Additionally, if the build option EXPERIMENTAL_DSN_INFO=yes is used,
the key material is included in the bounce message.
See also :
Update the affected package.
Risk factor :
Low / CVSS Base Score : 2.6