oss-security - Sv: [exim] CVE-2019-15846: Exim - local or remote attacker can execute programs with root privileges

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Message-ID: <005d01d564e3$cbf48090$63dd81b0$@sebbe.eu>
Date: Fri, 06 Sep 2019 20:50:37 +0200
From: "Sebastian Nielsen" <sebastian@...be.eu>
To: "'Heiko Schlittermann'" <hs@...marc.schlittermann.de>,
	"'oss-security'" <oss-security@...ts.openwall.com>,
	<exim-users@...m.org>
Subject: Sv: [exim] CVE-2019-15846: Exim - local or remote attacker can execute programs with root privileges

Shouldn't this be in connect ACL?
How would the deny in MAIL FROM prevent the exploit? What I have understand is that there is exploit in the SNI of the TLS negotiation, thus the whole connect attempt must be rejected right?

-----Ursprungligt meddelande-----
Från: Exim-users <exim-users-bounces+sebastian=sebbe.eu@...m.org> För Heiko Schlittermann via Exim-users
Skickat: den 6 september 2019 13:22
Till: oss-security <oss-security@...ts.openwall.com>; Exim Users <exim-users@...m.org>
Ämne: Re: [exim] CVE-2019-15846: Exim - local or remote attacker can execute programs with root privileges

An Update to the mitigation for the current CVE:

Add - as part of the mail ACL (the ACL referenced by the main config
option "acl_smtp_mail"):

     deny    condition = ${if eq{\\}{${substr{-1}{1}{$tls_in_sni}}}}
     deny    condition = ${if eq{\\}{${substr{-1}{1}{$tls_in_peerdn}}}}

This should prevent the currently known attack vector.

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