An environmental variable is some configuration parameter that all programs share. Multiple vulnerabilities have been discovered whereby the user of the Telnet client can carefully craft special environment variables designed to break into the machine. The Telnet server daemon will then attempt to load that shared library. This is a fairly old problem and most systems have been patched against it. Most instances of this alert are from scanners testing systems to see if they might be vulernable to this problem.
Defense Make sure the system is up to date with the latest patches.
Network ICE Corporation.