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Vulnerability of Exim: denial of service via ESMTP CHUNKING

Synthesis of the vulnerability 

An attacker can generate a fatal error via ESMTP CHUNKING of Exim, in order to trigger a denial of service.
Impacted products: Debian, Exim, Fedora, openSUSE Leap, SLES, Ubuntu.
Severity of this bulletin: 3/4.
Creation date: 27/11/2017.
Références of this threat: 2201, CVE-2017-16944, DSA-4053-1, FEDORA-2017-0032baa7d7, FEDORA-2017-0053bb9719, openSUSE-SU-2021:0677-1, openSUSE-SU-2021:0753-1, openSUSE-SU-2021:0754-1, USN-3493-1, USN-3499-1, VIGILANCE-VUL-24537.

Description of the vulnerability 

An attacker can generate a fatal error via ESMTP CHUNKING of Exim, in order to trigger a denial of service.
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This threat impacts software or systems such as Debian, Exim, Fedora, openSUSE Leap, SLES, Ubuntu.

Our Vigil@nce team determined that the severity of this computer threat is important.

The trust level is of type confirmed by the editor, with an origin of document.

An attacker with a expert ability can exploit this cybersecurity bulletin.

Solutions for this threat 

Exim: version 4.89.1.
The version 4.89.1 is fixed:
  http://ftp.exim.org/pub/exim/exim4/

Exim: patch for ESMTP CHUNKING.
A patch is indicated in information sources.

Exim: workaround for ESMTP CHUNKING.
A workaround is to set "chunking_advertise_host=".

Debian: new exim4 packages.
New packages are available:
  Debian 9: exim4 4.89-2+deb9u2

Fedora: new exim packages.
New packages are available:
  Fedora 26: exim 4.89-7.fc26
  Fedora 27: exim 4.89-7.fc27

openSUSE Leap 15.2: new exim packages.
New packages are available:
  openSUSE Leap 15.2: exim 4.94.2-lp152.8.3.1

SUSE LE 15 SP1: new exim packages.
New packages are available:
  SUSE LE 15 SP1: exim 4.94.2-bp151.2.4.1

SUSE LE 15 SP2: new exim packages.
New packages are available:
  SUSE LE 15 SP2: exim 4.94.2-bp152.6.4.1

Ubuntu: new exim4 packages.
New packages are available:
  Ubuntu 17.10: exim4 4.89-5ubuntu1.2
  Ubuntu 17.04: exim4 4.88-5ubuntu1.3
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