Postfix 2.5 before 2.5.4 and 2.6 before 2.6-20080814 delivers to a mailbox file even when this file is not owned by the recipient, which allows local users to read e-mail messages by creating a mailbox file corresponding to another user's account name.
Exploitability
AV:LAC:MAu:NImpact
C:PI:NA:N1.9/AV:L/AC:M/Au:N/C:P/I:N/A:N