As per upstream libreoffice advisory:

In LibreOffice 4.0.0 and later, a new feature was added for remote control capabilities in Impress. Users can run a smart phone
application to communicate with Impress over a custom protocol to switch slides and the like. By default whenever Impress is started, it immediately began listening on TCP port 1599 on all interfaces.

But there was a use after free bug in the code managing that port leaving LibreOffice vulnerable to  external attackers with access to that port where those external attackers could cause the deleted port manager to continue to process attacker supplied data.

All users are recommended to upgrade to LibreOffice 4.2.7 or 4.3.3.

The impress remote can be disabled by:

1. Open LibreOffice, go to "Tools -> Options..."
2. Select "LibreOffice Impress -> General"
3. Uncheck "Presentation -> Enable remote control"

External References:

http://www.libreoffice.org/about-us/security/advisories/cve-2014-3693