Debian: DSA-4053-1 Critical Exim4 Update: Remote Code Execution Threat

CVE-2017-16943

A use-after-free vulnerability was discovered in Exim's routines
responsible for parsing mail headers. A remote attacker can take
advantage of this flaw to cause Exim to crash, resulting in a denial
of service, or potentially for remote code execution.

CVE-2017-16944

It was discovered that Exim does not properly handle BDAT data
headers allowing a remote attacker to cause Exim to crash, resulting
in a denial of service.

For the stable distribution (stretch), these problems have been fixed in
version 4.89-2+deb9u2. Default installations disable advertising the
ESMTP CHUNKING extension and are not affected by these issues.

We recommend that you upgrade your exim4 packages.

For the detailed security status of exim4 please refer to its security
tracker page at:
https://security-tracker.debian.org/tracker/source-package/exim4

Further information about Debian Security Advisories, how to apply
these updates to your system and frequently asked questions can be
found...