It seems Symantec may have already fixed this exposure in it's NAVCE 7.51 Build 54. The following is quoted from their Platinum Support site.

"Long Path names
Symptom: Files and Folders with full path names longer than 259 characters would not be scanned, and no error was generated. In some cases, the client or server would crash.
Solution: Additional error checking was added to detect these file names, log the error in the NAV and NT Event Logs (Scan Omission) and to ignore the scanning of the file to prevent crashes."

DjM