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Date: Sat, 7 Sep 2019 08:23:33 +0200
From: Heiko Schlittermann <hs@...marc.schlittermann.de>
To: exim-users@...m.org
Cc: oss-security@...ts.openwall.com
Subject: Re: Sv: [exim] CVE-2019-15846: Exim - local or remote
 attacker can execute programs with root privileges

Phil Pennock <pdp@...m.org> (Sa 07 Sep 2019 02:52:56 CEST):
> The connect ACL won't protect you against STARTTLS usage, which is far
> more common for email than TLS-on-connect.
>
> I myself use the HELO ACL.

This doesn't seem to be sufficient, you can start "submitting" a message to
a remote Exim with the following sequence

    connect
        <-- 250
    EHLO …
        <-- 250
    STARTTLS
        <-- 220
    MAIL
        <-- 250

The client is free to skip the 2nd EHLO/HELO. Tested with OpenSSL
s_client -servername 'foobar\' -starttls smtp -connect …

    Best regards from Dresden/Germany
    Viele Grüße aus Dresden
    Heiko Schlittermann
--
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