The remote host is missing an update to wesnoth announced via advisory DSA 1386-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%201386-1

A problem has been discovered in the processing of chat messages. Overly long messages are truncated by the server to a fixed length, without paying attention to the multibyte characters. This leads to invalid UTF-8 on clients and causes an uncaught exception. Note that both wesnoth and the wesnoth server are affected. For the old stable distribution (sarge) this problem has been fixed in version 0.9.0-6 and in version 1.2.7-1~bpo31+1 of sarge-backports. For the stable distribution (etch) this problem has been fixed in version 1.2-2 and in version 1.2.7-1~bpo40+1 of etch-backports. For the unstable distribution (sid) this problem has been fixed in version 1.2.7-1. Packages for the oldstable mips architecture will be added to the archive later. We recommend that you upgrade your wesnoth packages.