Aucbvax.2952
fa.unix-wizards
utzoo!decvax!ucbvax!unix-wizards
Sat Sep  5 05:33:33 1981
Re: /usr/spool/mail
>From James.Gosling@CMU-10A Sat Sep  5 05:23:07 1981
If /usr/spool/mail is writable it's really easy to become super-user.

1. copy the shell to the file /usr/spool/mail/root
2. make it suid
3. send mail to root

When the mail is sent to root the delivery program only appends the mail to
the mailbox and chowns the file to root.  *poof* you have a suid root shell.
The easiest way to stop this is to not have /usr/spool/mail be writable.

					James.

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