The SMTP services SMTP greeting must not provide version information.

From Oracle Linux 5 Security Technical Implementation Guide

Associated with: CCI-000366

SV-63771r1_rule The SMTP services SMTP greeting must not provide version information.

Vulnerability discussion

The version of the SMTP service can be used by attackers to plan an attack based on vulnerabilities present in the specific version.

Check content

To check for the version of either sendmail or Postfix being displayed in the greeting: # telnet localhost 25 If a version number is displayed, this is a finding.

Fix text

Ensure sendmail or Postfix has been configured to mask the version information. Procedure for sendmail: Change the O SmtpGreetingMessage line in the /etc/mail/sendmail.cf file as noted below: O SmtpGreetingMessage=$j Sendmail $v/$Z; $b change it to: O SmtpGreetingMessage= Mail Server Ready ; $b for Postfix: Examine the "smtpd_banner" line of /etc/postfix/main.conf and remove any "$mail_version" entry on it or comment the entire "smtpd_banner" line to use the default value which does not display the version information.

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