source: http://www.securityfocus.com/bid/4059/info

AS/400 is a midrange computer platform developed by IBM. It is designed to be highly reliable and efficient, and uses the OS/400 operating system.

An information disclosure vulnerability has been reported to exist in OS/400 systems. An authenticated user may be able to obtain a list of all valid user accounts. The user must be running a 5250 emulator.

The user may, after authentication, access the 'System Request' menu and obtain a list of all object names of type USRPRF. The 'System Request' feature is installed by default.

This information may be useful in attempting further, intelligent attacks against the vulnerable server.

Sign-on to AS/400
Issue system request (Shift + Esc key)
Hit enter
Choose option 3, display current job
Choose option 13, display library list
Choose option 5 next to library QSYS
Scroll down to view names of all objects of type *USRPRF (user profile)