Security fix for CVE-2016-1531
==============================

All installations having Exim set-uid root and using 'perl_startup' are
vulnerable to a local privilege escalation. Any user who can start an
instance of Exim (and this is normally *any* user) can gain root
privileges.

The official fix is in Exim release 4.86.2. (tagged as exim-4_86_2)

For your convenience we released 4.85.2	    (tagged as exim-4_85_2)
                                 4.84.2	    (tagged as exim-4_84_2)

To support package maintainers on older systems we maintain (on a best
effort basis) GIT branches with backported patches for older releases:

				 exim-4_80_1+CVE-2016-1531
				 exim-4_82_1+CVE-2016-1531

(We didn't assign GIT tags, to indicate that's nothing real official.)


New options
-----------

We had to introduce two new configuration options:

    keep_environment =
    add_environment =

Both options are empty per default. That is, Exim cleans the complete
environment on startup. This affects Exim itself and any subprocesses,
as transports, that may call other programs via some alias mechanisms,
as routers (queryprogram), lookups, and so on.

** THIS MAY BREAK your existing installation **

If both options are not used in the configuration, Exim issues a warning
on startup. This warning disappears if at least one of these options is
used (even if set to an empty value).

keep_environment should contain a list of trusted environment variables.
(Do you trust PATH?). This may be a list of names and REs.

    keep_environment = ^LDAP_ : FOO_PATH

To add (or override) variables, you can use add_environment:

    add_environment = <; PATH=/sbin:/usr/sbin


New behaviour
-------------

Now Exim changes its working directory to / right after startup,
even before reading its configuration. (Later Exim changes its working
directory to $spool_directory, as usual.)

Exim only accepts an absolute configuration file path now, when using
the -C option.


Thank you for your understanding.

[Heiko Schlittermann <hs@schlittermann.de>]
