Re: [exim] CVE-2019-15846: Exim - local or remote attacker…

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Author: Sebastian Nielsen
Date:  
To: 'Heiko Schlittermann', 'oss-security', exim-users
Subject: Re: [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?

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Från: Exim-users <exim-users-bounces+sebastian=sebbe.eu@???> För Heiko Schlittermann via Exim-users
Skickat: den 6 september 2019 13:22
Till: oss-security <oss-security@???>; Exim Users <exim-users@???>
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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