Smail contains a flaw that may allow a malicious user to access abitrary file. The issue is triggered when a local attacker links their .forward file to a privileged file on the system (such as /etc/shadow). Once linked, connecting to the SMTP port and issuing the 'debug' command along with a few other crafted commands will allow the user to display the contents of the privileged file.
IBM BOKS passwd Arbitrary User Password Modification
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