Summary
The remote host is missing an update to the system as announced in the referenced advisory.
Solution
Update your system with the appropriate patches or software upgrades.
http://www.webmin.com/updates.html
http://www.vuxml.org/freebsd/ec89dc70-2515-11e2-8eda-000a5e1e33c6.html
Insight
The following package is affected: webmin