No IPv6 is supported from version 7
taken from following link
http://www.cisco.com/en/US/products/ps6553/products_qanda_item0900aecd803715bf.shtml
Q. When will Cisco ship IPv6 firewall capabilities to customers? What platforms will it support?
A. The Cisco IOS Software firewall feature set from Release 12.3(7)T and above as well as Cisco PIX? Firewall Software Version 7.0, including Cisco ASA 5500 Series adaptive security appliances, do support IPv6. Future releases of the Firewall Service Module (FWSM) on Cisco Catalyst 6500 Series switches will get IPv6 support in early 2006.
