QNAP has released Qfix v1.0.2 that is aimed to fix Shellshock for those who are still using the older firmware. QNAP adds the fix to the latest QTS 4.1.1 build 1003 firmware which the company has urged users who owns one of the NAS from QNAP to hit the update button to get the firmware to update.
However, if you still are using old firmware and are not yet ready to upgrade to the new firmware, then you should check the download section from QNP (link) to grab the fix so you can apply it manually. You would just need to select the model of your NAS and download the appropriate file and use the firmware update on your NAS to apply them. While it takes a little bit of work but it’s something that anyone who currently owns one of the NAS from QNAP should get as soon as possible so you can be protected.