Re: [exim] [oss-security] Sv: CVE-2019-15846: Exim - local o…

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Author: Heiko Schlittermann
Date:  
To: exim-users
CC: oss-security
Subject: Re: [exim] [oss-security] Sv: CVE-2019-15846: Exim - local or remote attacker can execute programs with root privileges
Phil Pennock <pdp@???> (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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