Werk #13897: Fix command injection vulnerability

Previously to this Werk an attacker who could control certain notification variables such as NOTIFICATIONTYPE or HOSTNAME was able to inject commands to the fall-back mail command. The commands were then executed as site user.

With this werk the variable MAIL_COMMAND is no longer available in notification scripts.

You can reduce the risk of exploitation with disabling the listening of the notification spooler (the default is disabled) (CEE/CME only feature).

All maintained versions (>=1.6) are subject to this vulnerability. It is likely that also previous versions were vulnerable.

To detect possible exploitation var/log/mknotifyd.log and var/log/notify.log can be checked for special shell characters like && and odd quoting.

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