Track note for CVE-2019-14899

We need to check how we want to actually handle this CVE. It is not an
issue direclty relatable to a source package. The vulnerability itself
works against various possible products, OpenVPN, WireGuard,
IKEv2/IPSec, systemd, ... Full details in
<https://www.openwall.com/lists/oss-security/2019/12/05/1>.