The remote host is missing an update to the system as announced in the referenced advisory FreeBSD-SA-05:16.zlib.asc

Upgrade your system to the appropriate stable release or security branch dated after the correction date https://secure1.securityspace.com/smysecure/catid.html?in=FreeBSD-SA-05:16.zlib.asc

zlib is a compression library used by numerous applications to provide data compression/decompression routines. An error in the handling of corrupt compressed data streams can result in a buffer being overflowed.