Bug 1517680 – CVE-2017-16943 exim: use-after-free in receive_msg function via vectors involving BDAT commands

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Bug 1517680 - (CVE-2017-16943) CVE-2017-16943 exim: use-after-free in receive_msg function via vectors involving BDAT commands

Summary:	CVE-2017-16943 exim: use-after-free in receive_msg function via vectors invol...

Status:	CLOSED NOTABUG

Aliases:	CVE-2017-16943

Product:	Security Response
Classification:	Other
Component:	vulnerability (Show other bugs)
Sub Component:
Version:	unspecified
Hardware:	All Linux

Priority	urgent Severity urgent
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Assigned To:	Red Hat Product Security
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URL:
Whiteboard:	impact=critical,public=20171123,repor...
Keywords:	Security

Depends On:	1517686 1517687
Blocks:
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Reported:	2017-11-27 03:47 EST by Adam Mariš
Modified:	2017-11-27 04:02 EST (History)
CC List:	4 users (show)

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Last Closed:	2017-11-27 04:02:33 EST
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Description Adam Mariš 2017-11-27 03:47:06 EST

The receive_msg function in receive.c in the SMTP daemon in Exim 4.88 and 4.89 allows remote attackers to execute arbitrary code or cause a denial of service (use-after-free) via vectors involving BDAT commands.

Upstream bug:

https://bugs.exim.org/show_bug.cgi?id=2199

Upstream patch:

https://git.exim.org/exim.git/commitdiff/4e6ae6235c68de243b1c2419027472d7659aa2b4

Comment 1 Adam Mariš 2017-11-27 03:54:14 EST

Created exim tracking bugs for this issue:

Affects: epel-all [bug 1517686]
Affects: fedora-all [bug 1517687]

Comment 2 Adam Mariš 2017-11-27 03:56:38 EST

Mitigation:

if you are running Exim 4.88 or newer, then in the main section of your Exim configuration, set:

chunking_advertise_hosts =

This disables advertising the ESMTP CHUNKING extension, making the BDAT verb unavailable and avoids letting an attacker apply the logic.

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