You can upgrade both the application software and the maintenance software. To upgrade the application software
http://www.cisco.com/en/US/docs/security/fwsm/fwsm11/configuration/guide/admin.html#wp1047381
To upgrade the maintenance software
http://www.cisco.com/en/US/docs/security/fwsm/fwsm11/configuration/guide/admin.html#wp1047550
The entire application and maintenance partitions are stored on the FTP or TFTP server. The images are downloaded and extracted to the application or maintenance partition depending on which image is being upgraded.
To upgrade the application partition, change the boot sequence to boot the module from the maintenance partition. The maintenance partition downloads and installs the application image. The supervisor engine must be executing the run-time image to provide network access to the maintenance partition.
