Is this a problem: “Bad encapsulated packet length from peer…”?

[DominikHoffmann]

Several times an hour I see something like this in my OpenVPN log:

Apr 30 07:15:01	openvpn	15357	78.153.140.177:49068 WARNING: Bad encapsulated packet length from peer (18245), which must be > 0 and <= 1800 -- please ensure that --tun-mtu or --link-mtu is equal on both peers -- this condition could also indicate a possible active attack on the TCP link -- [Attempting restart...]

Is this really just an attempt to break down my door with a buffer overflow and, because it is caught, not a problem? The IP address is definitely not one under my control.