Hello!

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commit 5b327a2d6192adbabb5b98bc3a78eb8402bd6d1d
Author: Leo Famulari <leo@famulari.name>
Date:   Sun Nov 26 15:23:13 2017 -0500

    gnu: exim: Fix CVE-2017-16943.
    
    * gnu/packages/patches/exim-CVE-2017-16943.patch: New file.
    * gnu/local.mk (dist_patch_DATA): Add it.
    * gnu/packages/mail.scm (exim)[source]: Use it.
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This commit fixes a bug in Exim that allows attackers to gain remote
code execution on your server. If you are using Exim from the Guix
package, please update it as soon as possible.

For more information:

https://bugs.exim.org/show_bug.cgi?id=2199
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-16943