https://bugs.exim.org/show_bug.cgi?id=3099

--- Comment #4 from Heiko Schlichting <[email protected]> ---
I can confirm this bug. It looks like a serious security issue to me. There
should be a CVE number for it and it should definitely be fixed before Exim
4.98 is released.

Can be reproduced as follows:

-----

acl_smtp_mime = acl_check_mime

acl_check_mime:

    deny     message   = This message contains an attachment of a type that we
do not accept ($mime_filename).
             condition = ${if match {${lc:$mime_filename}}{\N\.exe$\N}}

    accept

-----

Sending the following mails with "exim -t". The second mail should NOT be
accepted.

---------------------------- deny ---------------------------

From: [email protected]
To: [email protected]
Subject: Bug 3099 (1)
MIME-Version: 1.0
Content-Type: multipart/mixed; boundary="----=_MIME_BOUNDARY_000_695039"

------=_MIME_BOUNDARY_000_695039
Content-Type: text/plain

This is a test mailing
------=_MIME_BOUNDARY_000_695039
Content-Type: application/octet-stream
Content-Disposition: attachment;
    filename="example.exe"
Content-Transfer-Encoding: BASE64

QmVpc3BpZWwK

------=_MIME_BOUNDARY_000_695039--

---------------------------- accept ---------------------------

From: [email protected]
To: [email protected]
Subject: Bug 3099 (2)
MIME-Version: 1.0
Content-Type: multipart/mixed; boundary="----=_MIME_BOUNDARY_000_695039"

------=_MIME_BOUNDARY_000_695039
Content-Type: text/plain

This is a test mailing
------=_MIME_BOUNDARY_000_695039
Content-Type: application/octet-stream
Content-Disposition: attachment;
    filename*0*="example3";
    filename*1*=".exe"
Content-Transfer-Encoding: BASE64

QmVpc3BpZWwK

------=_MIME_BOUNDARY_000_695039--

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